Skip to main content
  • Research Paper
  • Open access
  • Published:

The Early Childhood Education Workforce in Europe Between Divergencies and Emergencies


Across and beyond Europe, demographic, social and economic pressures both at the macro and the micro level are impacting on the work contexts of early childhood educators. Alongside heightened drives towards expansion and increasing regulation of the field, expectations are intensifying. Additionally, goals and targets for higher education and vocational education at the European policy level are generating restructurings of the national qualification systems for work in the early childhood field. In this dynamic context of change the SEEPRO (Early Education/care and Professionalisation in Europe) study, based at the State Institute of Early Childhood Research in Munich and funded by the German Federal Ministry of Family and Youth Affairs, set out to map the qualification requirements and workplace settings of early years practitioners in their country-specific context. Similarities and differences across the 27 countries of the European Union were documented and analysed. The findings of the study show considerable divergencies across Europe in terms of formal education and training requirements and the desired professional profiles for working with young children. Against this background of diversity, similarities in terms of workforce emergencies and challenges have also emerged: one is a common lack of truly flexible and inclusive pathways linked to formal professional recognition and status for all practitioners in the field; another is the continuing need to seek more effective ways of including men in the early childhood workforce.

Policy and Research Context

The project team members were Pamela Oberhuemer, IFP Munich (lead researcher); Inge Schreyer, IFP Munich; and Michelle J. Neuman, Washington DC.

Early childhood educators across and beyond Europe are experiencing rapidly changing work contexts both at the macro and micro level. Driven primarily by demographic, economic and social pressures, awareness of the advantages of a well-resourced system of early childhood education and care (ECEC) is growing, with beneficial effects seen in terms of family and employment policies, education policy and also long-term economic policy. Within this overall context of expansion and heightened attention, combined in most cases with increasing regulation of the field, expectations directed towards professional early childhood educators are intensifying. It is therefore not surprising that the early childhood workforce is a focus of concern for researchers across countries. Some have consistently critiqued structural injustices within the makeup of the workforce (Moss, 2006; 2008), while others have pinpointed the contradictory effects that the ‘regulatory gaze’ (Osgood, 2006) may have on practitioners’ understandings of professionalism (Oberhuemer, 2005; Ortlipp, Arthur, & Woodrow, 2011). Some have investigated possible links between the professional education of practitioners and characteristics of the setting or children’s social and cognitive achievements (e.g., Barnett, 2004; Early et al., 2006; Kelley & Camilli, 2007), while others have focused on gender disparities within the workforce (Cameron, 2006; Cameron, Moss, & Owen, 1999) and the low levels of pay (e.g. Barnett, 2003). Both research-driven calls for workforce reforms in countries where structural discrepancies are particularly pronounced, such as the US and the UK (Kagan, Kauerz, & Tarrant, 2007; Moss, 2008), and also international policy reviews across a wide range of early childhood systems (OECD, 2006; UNICEF, 2008), are unanimous in their emphasis on the key role of the workforce in maintaining and improving the quality of early childhood education and care.

Although the qualifications and workplace settings of personnel in early childhood centres are recognized as perhaps the most significant contributory factor towards achieving and maintaining high quality services, there is little research which has looked systematically at this aspect of early childhood provision across Europe. In this article I draw primarily on a recent study of the systems of early education/care and professionalization in the 27 European Union countries which aimed to redress this gap (Oberhuemer, Schreyer, & Neuman, 2010). The findings suggest that not only are the divergencies between these systems considerable, but also that selected workforce issues could be construed as ‘emergencies’ in terms of seriously improving the initial and ongoing professional development and career opportunities for those working with young children.

The SEEPRO Study: Aims and Methodology

The SEEPRO study (2006-2009) was based at the State Institute of Early Childhood Research in Munich and received funding from the German Federal Ministry for Family and Youth Affairs. The reasons for carrying out this study included the following (Oberhuemer, in press): (1) although student and practitioner mobility in Europe is on the increase, in Germany (and presumably in other countries) there is only limited knowledge among those involved in early years training, field support and administration about current qualification requirements, professional profiles and workplace settings of ECEC staff in other European countries; (2) although professional circles show a keen interest in European developments as a frame of reference for critical analyses of the system of ECEC provision and professionalization in their own country, available resources for these reflexive processes are limited; (3) although a rapidly increasing number of higher education institutions in Germany are now offering first-time Bachelor-level qualifications in early childhood education beyond the stipulated post-secondary level of training, the required and desired professional profile is as yet unclear.

Accordingly, the main aims were:

  • to map the qualification requirements and workplace settings of early years practitioners in their country-specific context;

  • to trace similarities and differences in professional profiles across countries; and

  • to pinpoint key workforce issues in a cross-national perspective.

During the main part of the study, the focus was on the countries which joined the European Union in 2004 (Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Romania, Poland, Slovak Republic, Slovenia) and in 2007 (Bulgaria, Romania). For these countries, our aim was to access and systematise data on the staffing of early childhood services and to present these within the country-specific context. In a second step, the country profiles of an earlier IFP study in the EU15 were revised in close cooperation with national experts. The research methods for the 12 post-2004 countries included commissioning reports by national experts which served as a frame of reference for five-day research visits, during which semi-structured interviews were held with a range of representatives and stakeholders in each country. These five-day research visits were organised by a country coordinator. The interviews were held mainly in English, sometimes with the help of a local interpreter. Beyond this, document analysis and relevant data banks (Eurydice, Eurostat, OECD) were used as additional sources of information. Each of the SEEPRO country profiles was sent to our co-operation partners for review, clarification and amendment. The interviews with a well-balanced range of partners in each country provided direct insight into early childhood systems. They not only opened up a variety of perspectives on our research questions, they were also essential for clarifying terms and thus for interpreting the data.

The SEEPRO study revealed that European-level goals and targets for higher education and vocational education have generated a number of restructurings of the national qualification systems for work in the early childhood field (Oberhuemer, Schreyer, & Neuman, 2010). The current picture regarding minimum qualification requirements across the 27 countries will now be presented.

Professional Education/Training for Work with 3 to 6 Year Olds: A Common Core with Considerable Variations

In the greater majority of countries, an ISCED 5-level qualification is the minimum requirement for working as a core practitioner (responsible for a group of children or for the centre) with children aged three years up to compulsory schooling. This is mostly a Bachelor-level degree awarded at the end of a three-year full-time course of study at a specialised university department or a university college. In all cases the focus is on education and pedagogy, although not necessarily only on early childhood pedagogy. In an increasing number of countries the requirements are higher in terms of the duration of study or the formal qualification. For example, since 2007, it is now a requirement in Portugal to have a four- to four-and-a-half year Master’s degree for work in both public and private kindergartens for this age-group. (This is now also the case in Iceland, a non-EU country.) In Cyprus, Greece, Italy and Luxembourg, prospective early childhood educators undertake not three but four years of professional studies — although in Italy and Luxembourg these are not exclusively focused on the early years. In Denmark and Sweden, the core practitioners working in early childhood settings follow a three-and-a-half year course of studies; and in France, the requirement is a post-graduate qualification following the successful completion of a three-year university degree. In the case of England (and Scotland), the three-year requirement at higher education level applies only for a sub-group of the ECEC workforce — for teachers working in the state-maintained sector with 3 and 4 year olds. However, it does not apply for the practitioners working in the significantly larger private, voluntary and independent (PVI) sector. There are now only five countries in the 27 EU states where a Bachelor degree is not (yet) a requirement for working with the 3 to 6 age-group: Germany, Austria, the Czech Republic, the Slovak Republic and Malta. However, in all of these countries, there have been recent moves to introduce more higher education level qualification routes for work in early childhood settings.

Qualification Requirements for Work with Children up to 3 Years: Widely Divergent Approaches

Although there is in some countries a similar drive to upgrade the minimum qualification requirements for work with children from birth to three, the starting-points are very diverse, both in terms of disciplinary orientation and formal level. Whereas in the Nordic EU countries (Denmark, Finland, Sweden), the Baltic countries (Estonia, Latvia, Lithuania) and the central European state of Slovenia the core practitioners are required to have an ISCED 5-level qualification with an educational/ pedagogic orientation, in several other countries (e.g. Belgium, Bulgaria, Czech Republic, France, Poland, Portugal, Romania) the requirement is a health/care qualification, sometimes without a specific focus on work with very young children. These health/care qualification requirements are also at different formal levels; some are post-secondary awards at ISCED 4-level (Poland, Romania), while others are upper secondary qualifications (Italy, Netherlands). And in a few countries, there are no minimum requirements for working with this age-group at all. Until very recently, this has consistently been the case in Ireland and Malta, both countries with largely market-led private childcare sectors, and also in Belgium (Flanders) for work in private infant-toddler centres.

Professional Profiles: Another Case of Variation and Diversity

In the SEEPRO study we identified six main professional profiles of core practitioners.

The first (although this order does not have hierarchical significance) is the early childhood professional with a specialist education and training to work with children across the age-span from birth up to compulsory schooling. One example is the ‘kindergarten teacher’ in Finland. A lastentarhanopettaja works either in an early childhood centre for children from birth to 6 — in a multi-professional team with mainly health/care professionals — or (independently) in a pre-school class for 6 to 7 year olds, which may be located in an early childhood centre or in a primary school. Another example is the ‘early childhood educator’ in Slovenia. A vzgotijelj may work — as in Finland — in an early childhood centre for children from birth to 6, or in the first class of primary school alongside a teacher.

The second is the pre-primary professional. These practitioners are not trained for work with under-threes; their workplace settings are located within the education system and they are responsible for a group/class of children in the two or three years immediately preceding compulsory schooling. The kleuterleidster or institutrice de maternelle in the Flemish-speaking and French-speaking regions of Belgium are qualified in this way, as are the core practitioners in Cyprus (nipiagogio), the Czech Republic (ucitelka), Greece (nipiagogos), Hungary (óvodapedagógus), Italy (insegnante di scuola dell’infanziä), Malta (kindergarten assistant), Poland (nauczyciel wychowania przedszkolnego) and Romania (educatoare). All are educated/trained at higher education level.

The third category is that of the pre-primary and primary school professional. In most cases these are teachers trained for work in primary schools and pre-primary settings within the education sector, such as the professeur des écoles in France or the primary school teacher in Ireland, who also works with 4 and 5 year olds in school-based infant classes preceding compulsory schooling at age 6. One inherent problem of this approach is that schools are compulsory and a school-biased professional training curriculum may (and often does) pay too little attention to the non-compulsory pre-school years.

The fourth kind of profile is that of the social pedagogy professional. This is a much broader profile to be found, for example, in Denmark (paedagog) and Germany (Erzieherin). As core professionals, they are not only trained to work with young children but also with school-age children and young people and (in the case of Denmark) with adults with special needs. The main professional focus is on social pedagogy or social work outside the education system.

A fifth category can be described as the infant-toddler professional. In Hungary, for example, the core practitioners who work with under-threes are trained specifically to work in a pedagogical way with this age-group, as is the educatrice in Italy.

The final group of practitioners are the health/care professionals working with under-threes. In some countries this may be a child-focused qualification (e.g. paediatric nurse or children’s nurse, as in France, Luxembourg and Romania), in others it may be a general health or social care qualification for working with people of all ages (as in Bulgaria, Poland and Portugal).

In some cases these core practitioners are supported by a fully qualified assistant with an early years specialist focus, as is the case in Slovenia. In other countries (e.g. Cyprus, Greece, Ireland), they work alone with a group of children, without any kind of qualified or non-qualified assistant except for children with special needs. In the Baltic countries there are few assistants to be found on a daily basis, but regular support is provided by tertiary-level trained specialists in specific areas of learning (e.g. music, physical education).

Emerging Dilemmas and Challenges

These divergent understandings and policy approaches towards the professional preparation of staff working with young children in education and care settings raise a number of questions regarding decisions about future professionalization policies. What is the desired balance between pedagogy and other disciplines; between age-focused, specialist and generalist approaches; between highly qualified core practitioners and less qualified auxiliary staff? Can coherent professional profiles be achieved within systems which are not fully integrated, i.e. where one ministry is responsible for the entire early childhood sector and also public funding streams and staffing policies are the same across the sector? Will decisions be taken in countries with split systems (e.g. Belgium, Bulgaria, Italy, Luxembourg, Portugal, Romania) or partially split systems (e.g. the UK countries) to create more unity, coherence and consistently high-level professional requirements across the sector? Will parity be reached with primary school teachers in terms of qualification level, status and pay? Two workforce challenges in particular could be described as pressing or ‘emergency’ issues: developing more inclusive approaches towards professionalization and improving the gender balance, i.e. attracting more men into the workforce. I shall now look at these two issues more closely, dwelling on selected countries in which there are active moves to redress imbalances.

Adopting More Inclusive Professionalization Strategies

England and Ireland are countries in which the staffing patterns reflect a traditional location of early childhood services within a split system of administrative responsibility for ‘education’ and ‘childcare’. In both countries there is a strong representation of privately run provision within the childcare sectors, with weak staffing requirements. There is no tradition in either country of a highly professionalised workforce across the age-range birth to 5/6 years. Although there have been recent moves towards stronger regulatory integration across the two sectors, this has not taken place in the same way for all aspects of the early childhood system, most notably for the staffing of early education and care services up to compulsory school age (officially at age 5 in England and 6 in Ireland). Notable shifts have taken place in both countries in recent years.

In England, a government endorsed strategy aiming to create a ‘graduate led’ early years workforce, particularly in the private, voluntary and independent (PVI) sector, was introduced in 2005 as part of a Children’s Workforce Strategy. The following year, an award called the Early Years Professional Status was launched, based on 39 national standards. Four government-funded qualifying routes of varying length, depending on the candidate’s prior qualification, prepare graduates (also those with a two-year foundation degree) to take on a lead role in settings in the PVI sector, where requirements traditionally have been much lower than those for the maintained education sector, even for those leading a centre. They are particularly responsible for implementing the Early Years Foundation Stage, a revised curricular framework for children from birth to five introduced in 2008. A recent national survey has shown that 62 per cent of Early Years Professionals working in the field are in fact employed in the PVI sector (CWDC, 2011a). Already there are over 7000 accredited EYPs and currently over 3000 are undertaking training. The strategy is being continued under the coalition government which came to power in May 2010 with a programme entitled “New leaders in Early Years” (CWDC, 2011b). However, a number of problems have been emerging since the inception of the EYPS strategy. These include issues of workforce inclusion in terms of status (which is not on a par with that of qualified teachers), of pay (which is lower than that for teachers and with no national agreement), and of professional recognition — both among colleagues and employers (see e.g. Hevey, 2010; Lloyd & Hallet, 2010). It seems that a well-meaning reform has not been fully thought through in terms of the consequences for the profession.

In Ireland, early years practitioners outside the education system — i.e. those working in the predominantly privately-run childcare sector mainly for children under 4 years of age — have not been required to have a specific minimum qualification, whereas teachers working with 4 and 5 year olds in the (non-compulsory) infant classes in primary school have a three-year Bachelor-level teaching qualification, but without a strong specialisation in early years pedagogy. A recent survey of the Irish workforce showed that 12 per cent of the childcare workforce does not have any accredited childcare-related qualification (OMCYA, 2009). In order to improve opportunities for staff with no or low-level qualifications, a new set of occupational profiles linked into the National Qualifications Framework of Ireland now enable early childhood practitioners to progress through various stages (Basic, Intermediate, Experienced, Advanced, Expert), ranging from ICED 3 to ISCED 5, thus opening up pathways for career progression. Since a new policy move in 2009 to introduced entitlement for 3 year olds to a fee-free year of pre-school provision, however, the leaders of (private) settings offering this provision are now required to hold a specialised certificate equivalent to ISCED level 4, and it is expected that this requirement will be upgraded in the not-too-distant future (OMCYA, 2009). However, in general the occupational profiles still have the status of non-binding recommendations.

Improving Gender Parity Including Men in the Workforce

Fifteen years ago, one of 40 targets formulated by a network of early childhood experts from the then 12 countries of the European Community was that “20 per cent of staff employed in collective services should be men.” (European Commission Network on Childcare, 1996, p. 24). According to interviews held and documents analysed during the SEEPRO project, in 17 of the 27 member states of the EU, male workers represent under one per cent of the workforce (Oberhuemer, Schreyer, & Neuman, 2010). No country has reached the 20 per cent target. However, in certain countries, moves are under way to improve this situation.

The country with the highest and a rising proportion of men in professional education/training for work in the field is Denmark, where 25 per cent of enrolled students are men. Denmark also has the highest and a rising proportion of men in the ECEC workforce. In 2009, men accounted for 7 per cent of staff in centres for under-threes, 11 per cent in kindergartens for 3 to 6 year olds and 13 per cent in mixed-age centres for children from birth to 6. How can this be explained? Among the possibilities are the following: Nearly 20 years ago (in 1992, a three-prong specialist approach to professional education/training was replaced by a broad, generalist professional profile. This broader profile generates increased labour market flexibility, since the qualification as paedagog is not linked to just one field of employment. In addition, the Danish education system offers very inclusive academic and non-academic pathways into the higher education professional training institutions. Finally, the employment conditions of paedagoger are generally favourable, offering a secure job with good prospects and a comparatively good salary.

In Germany, a current government-funded initiative is attempting to raise the low but rising number of males in the workforce. According to the German Federal Statistics Office, in 2010 men accounted for 3.4 per cent of staff in early childhood provision. However, in urban areas (e.g. in the cities of Bremen and Frankfurt), this proportion can be significantly higher — up to 9 per cent. Research commissioned by the Federal Ministry for Family and Youth Affairs showed that service providers, centre leaders and parents clearly wish to see more men in early childhood provision (Koordinationsstelle Männer in Kitas, 2011). Within an overall policy framework of equal opportunities, a co-ordination office and a website have been set up, and a new government initiative (2011–2013) is providing funding to support 16 pilot initiatives aimed at strengthening regional networking in 13 of the 16 federal states (Länder). Some 1300 early childhood centres are involved in these initiatives. Strategic consultancy services are provided to improve the recruitment of men into the early years workforce (Koordinationsstelle Männer in Kitas, 2011).

Overall, however, apart from one or two exceptions such as initiatives in (non-EU) Norway, the UK and in Belgium, recruiting men into the workforce has not had significant policy attention.

A Workforce between Divergencies and Emergencies

The SEEPRO study revealed that both national and European-level goals and targets for higher education and vocational education are generating restructurings of the national qualification systems for work in the early childhood field (Oberhuemer, Schreyer, & Neuman, 2010). This brief overview of selected professionalization and workforce policies related to early childhood education and care has attempted to illustrate just some of the diversities across Europe. It is unlikely that a similar cross-national perspective on the teaching workforce in primary schools would reveal such divergent approaches towards qualification requirements, training approaches, professional profiles, and recruitment and support systems. While there have been considerable steps forward, in many countries there remain significant structural and conceptual divisions across the early childhood sector — even at the beginning of the second decade of the 21st century. This year, for the first time, the European Commission issued a communication focused solely on early childhood education and care (European Commission, 2011). Among the proposed issues for cooperation among Member States are the following: Promoting the professionalization of ECEC staff: what qualifications are needed for which functions; developing policies to attract, educate and retain suitably qualified staff to ECEC; improving the gender balance of ECEC staff; moving towards ECEC systems which integrate care and education, and improve quality, equity and system efficiency. Implementing these goals in the current economic climate remains a challenge for the future.


  • Barnett, W. S. (2003, March). Low wages = low quality: Solving the real preschool teacher crisis (Preschool policy matters Issue No. 3). Retrieved May 15, 2011, from

  • Barnett, W. S. (Rev. ed.). (2004, December). Better teachers, better preschools: Student achievement linked to teacher qualifications (Preschool policy matters Issue No. 2). Retrieved May 15, 2011, from

  • Cameron, C. (2006). Men in the nursery revisited: Issues of male workers and professionalism. Contemporary Issues in Early Childhood, 7 (1) 68–79.

    Article  Google Scholar 

  • Cameron, C., Moss, P., & Owen, C. (1999). Men in the nursery: Gender and caring work. London, UK: Paul Chapman Publishing.

    Google Scholar 

  • Children’s Workforce Development Council [CWDC]. (2011a, January 26). First national survey of early years graduate leaders identifies positive impacts. CWDC news e-bulletin. Retrieved May 18, 2011 from

  • Children’s Workforce Development Council [CWDC]. (2011b, May 4). New leaders in early years programme recruiting now. CWDC News e-bulletin. Retrieved May 20, 2011 from

  • Department of Education and Science. (2009). Developing the workforce in the early childhood care and education sector. Background discussion paper. Retrieved May 19, 2011 from

  • Early, D. M., Bryant, D. M., Pianta, R. C., Clifford, R. M., Burchinal, M. R., Ritchie, S., et al. (2006). Are teachers’ education, major, and credentials related to classroom quality and children’s academic gains in pre-kindergarten? Early Childhood Research Quarterly, 21 (2) 174–195.

    Article  Google Scholar 

  • European Commission. (2011, February 17). Early childhood education and care: Providing all our children with the best start for the world of tomorrow. Communication from the Commission. Retrieved May 21, 2011 from

  • Hevey, D. (2010). Developing a new profession: A case study. Literacy Information and Computer Education Journal (LICEJ), 1 (3) 233–242.

    Google Scholar 

  • Kagan, S. L., Kauerz, K., & Tarrant, K. (2007). The early care and education teaching workforce at the fulcrum: An agenda for reform. New York: Teachers College Press.

    Google Scholar 

  • Kelley, P., & Camilli, G. (2007). The impact of teacher education on outcomes in center-based early childhood education programs: A meta-analysis. Retrieved May 15, 2011, from

  • Koordinationsstelle Männer in Kitas. (2011). Male educators in Kitas. Retrieved May 20, 2011, from;cHash=2b6e914181598260c1d292bad39740c9

  • Lloyd, E., & Hallet, E. (2010). Professionalising the early childhood workforce in England: Work in progress or missed opportunity? Contemporary Issues in Early Childhood, 11 (1) 75–88.

    Article  Google Scholar 

  • Lohmander, M. K. (2004). The fading of a teaching profession? Reforms of early childhood teacher education in Sweden. Early Years: An International Journal of Research and Development, 24 (1) 23–34.

    Article  Google Scholar 

  • Moss, P. (2006). Structures, understandings and discourses: Possibilities for re-envisioning the early childhood worker. Contemporary Issues in Early Childhood, 7 (1) 30–41.

    Article  Google Scholar 

  • Moss, P. (2008). The democratic and reflective professional: Rethinking and reforming the early years workforce. In L. Miller & C. Cable (Eds.), Professionalism in the early years (pp. 121–130). London, UK: Hodder Education.

    Google Scholar 

  • Oberhuemer, P. (2005). Conceptualising the early childhood pedagogue: Policy approaches and issues of professionalism. European Early Childhood Education Research Journal, 13 (1) 5–16.

    Article  Google Scholar 

  • Oberhuemer, P. (in press). Radical reconstructions? Early childhood workforce profiles in changing European ECEC systems. In L. Miller, C. Dalli & M. Urban (Eds.), Early Childhood Grows Up: Towards a Critical Ecology of the Profession. Dordrecht: Springer Netherlands.

  • Oberhuemer, P., Schreyer, I., & Neuman, M. J. (2010). Professionals in early childhood education and care systems: European profiles and perspectives. Opladen & Farmington Hills, MI: Barbara Budrich.

    Google Scholar 

  • Ortlipp, M., Arthur, L., & Woodrow, C. (2011). Discourses of the early years learning framework: Constructing the early childhood professional. Contemporary Issues in Early Childhood, 12 (1) 56–70.

    Article  Google Scholar 

  • Osgood, J. (2006). Deconstructing professionalism in early childhood education: Resisting the regulatory gaze. Contemporary Issues in Early Childhood, 7 (1) 5–14.

    Article  Google Scholar 

  • UNICEF. (2009). The child care transition: A league table of early childhood education and care in economically advanced countries (Innocenti Report Card 8). Retrieved May 16, 2011 from

Download references

Author information

Authors and Affiliations


Corresponding author

Correspondence to Pamela Oberhuemer.

Rights and permissions

Open Access  This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.

The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

To view a copy of this licence, visit

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Oberhuemer, P. The Early Childhood Education Workforce in Europe Between Divergencies and Emergencies. ICEP 5, 55–63 (2011).

Download citation

  • Published:

  • Issue Date:

  • DOI:

Key words