7I Granovetter, M. S. The Strength of Weak Ties[J].The American Journal of Sociology,1973,78(6): 1360-1380.
8KESSLER C.Cooperative language learning:a teacher's re-source book[M]. Englewood Cliffs,NJ: Prentice Hall Regents,1992.
9MCGROARTY M. Cooperative learning and second languageacquisition [C]// HOLT D D, Cooperative learning. Washing-ton ,DC : Center for Applied Linguistics&ERIC clearinghouseon Language and Linguistics, 1993.
10VYGOTSKY L S. Mind in society[M].Cambridge, Mass : MITPress, 1978.