2Deborah E. Allen and Barbara J. Dueh. Thinking Toward Solutions: Problem - Based Learning Activities for General Biology. Saunders College Publishing, 1998.
3Dorothy H. Evensen and Cindy E. Hmelo. Problem- Based Learning: A Research Perspective on Learning Interactions.Lawrence Erlbaum Associates, Publishers, 2000.
4Christopher K Knapper and Arthur J Cropley. Lifelong Learning and Higher Education. Kogan Page, 1991.