5Danlelle Colardyn,Jens Bjomavold. Validation of Formal,Non-Formal and InformalLearning: policy and practices inEU Member States[J]. European Journal of Education,2004:69-89.
6Brian L. Gerber,Edmund A. Marek & Ann M. L. Cavallo. De-velopment of an informal learning opportunities assay[J].International Journal of Science Education,2001,23(6).
7LIVINGSTONE David. W. Adults informal learning:defini-tions,findings,gaps and future research[J]. New Approach-es to lifelong learning Working Paper,2001,21(3).