Science direct, european policies (Januari 2012). "European policies on lifelong learning in between competitiveness enhancement and social stability reinforcement". Procedia - Social and Behavioral Sciences. 4th WORLD CONFERENCE ON EDUCATIONAL SCIENCES (WCES-2012) 02-05 February 2012 Barcelona, Spain (dalam bahasa Inggris). 46: 548–553. doi:10.1016/j.sbspro.2012.05.158.Parameter |s2cid= yang tidak diketahui akan diabaikan (bantuan)
González, Sheila; Bonal, Xavier (2021). "COVID-19 school closures and cumulative disadvantage: Assessing the learning gap in formal, informal and non-formal education". European Journal of Education (dalam bahasa Inggris). 56 (4): 607–622. doi:10.1111/ejed.12476. hdl:2445/191589. ISSN0141-8211.
González, Sheila; Bonal, Xavier (2021). "COVID-19 school closures and cumulative disadvantage: Assessing the learning gap in formal, informal and non-formal education". European Journal of Education (dalam bahasa Inggris). 56 (4): 607–622. doi:10.1111/ejed.12476. hdl:2445/191589. ISSN0141-8211.
González, Sheila; Bonal, Xavier (2021). "COVID-19 school closures and cumulative disadvantage: Assessing the learning gap in formal, informal and non-formal education". European Journal of Education (dalam bahasa Inggris). 56 (4): 607–622. doi:10.1111/ejed.12476. hdl:2445/191589. ISSN0141-8211.