3Ofra Nir-Gal (2002),Distance Learning:The Role of the Teacher in a Virtual Learning Environment[EB/OL].http://web.macam98.ac.il/～ nirgalo/a-publish-study/E-%20 Leaming-m&m.htm.
4Tagg,A.C.& Dickenson,J.A.(1995).Tutor messaging and its effectiveness in encouraging student participation on computer conferences[J].Journal of Distance Education,X(2),33-55.
5Dennis Gooler et al.Teacher Competence in Using Technologies:The Next Big Question[EB/OL].http://www.prel.org/products/Products/teacher-competence htm.
