AJJM Ruijssenaars Editor

J.H.M. Hamers, Department of Education, Utrecht University, P.O. Box 80.140, 3508 TC Utrecht, the Netherlands. K. Sijtsma, Faculty of Psychology and Education, Vrije Universiteit Amsterdam, De Boelelaan 1081,1081 HV Amsterdam, the Netherlands. A.J.J.M. Ruijssenaars, Department of Education, University of Leuven, Vesaliusstraat 2, 3000 Leuven, Belgium.