2Kaufman DM. Problem-based learning-time to step back[ J ] . Med Educ, 2003,34 ( 7 ): 509-511.
3Seneviratne RD, Samarasekera DD, Karunathilake IM, et al. Students perception of problem based learning in the medical curriculum of the faculty of medicine, university of Colombo[ J ] . Ann Acad Med Singapore,2001,30 ( 4 ): 379-381.
4Dolmans DH, De Grave W, Wolthagen IH, et al. Problem-based learning: future challenges for educational practice and research [ J] .Med Educ, 2005,39 ( 7 ) : 732-741.