4Sherry, L. Issues in Distance Learning [J].International Journal of Educational Telecommunicatiom,1996,1 (4): 337-365.
5Garrison, D.K. An analysis and evaluation of audio teleconferencing to facilitate education at a distance[J]. The American Journal of Distance Education,1990,4(3):16-23.
6ChizmarJ.F.,Walbert, M.S.Web-Based Learning Environments Guided by Principles of Good Teaching Practice[J].The Journal of Economic Education,1999, (30): 248-259.
7DtiscolL M. Psychology of learning for instruction( 2nd edition) [M].New York:Allyn & Bacon, 2000.
