4Rheingold H. Virtual Community: Homesteading on the Electronic Frontier, Reading, Mass [ M . Massachusetts : Addison-Wesley, 1993.
5Hagel J H, Armstrong A G. Net Gain: Expanding Markets Through Virtual Communities [ M ]. Boston, MA : Harvard Business School Press, 1997.
6Zhang Z. Feeling the sense of community in social networking usage [ J ]. IEEE Transactions on Engineering Management, 2010, 57: 225-239.
7Katz M, Shapiro C. Product introduction with network externalities [ J]. The Journal of Industrial Economics, 1992, 40: 55-83.
8Gu B, Konana P, Rajagopalan B, et al. Competition among virtual communities and user valuation: the case of investing-related communities [ J ]. Information Systems Research, 2007, 18: 68-85.
9Hung S W, Cheng M J. Are you ready for knowledge sharing? An empirical study of virtual communities [ J ]. Computers & Education, 2013, 62(MAR) : 8-17.
10Shu W, Chuang Y H. Why people share knowledge in virtual communities? [ J ]. Social Behavior and Personality, 2011, 39 ( 5 ) : 671-690.
