1Cochran, K. F., DeRuite, J. A., & King, R. A. 1993. Pedagogical content knowing: An integra- tive model for teacher preparation [J]. Journal of Teacher Education, 44(4): 263-272.
2Patton, M. Q. 1990. Qualitative Evaluation and Re- search Methods [M]. New York: Sage Publications, Inc.
3Shulman, L. S. 1987. Knowledge and teaching: Foun- dations of the new reform [J]: Harvard Education- al Review, 57(1): 1-23.