5Kai Lung Hui, Patrick Y. K Chau. Classifying Digital Products[J]. Communication of the ACM, 2002(6):73 -79.
6Y Y Yao. Granular Computing: Basic Issues and Possible Solutions [A]. Proceedings of the 5th Joint Conference on Information Sciences [C]. Atlantic City. New Jersey. USA, 2000:186- 189.
7Katz M L, Shapiro C. Network Externalities,Competition and Compatibility[J]. America Economic Review, 1985, 75(3) :424 - 400.
8Liebowitz S J, Stephen E. Network Externality: An Uncommon Tragedy[J]. Journal of Economic Perspectives, 1994, 8(2):133 - 150.
9Katz M L, Shapiro C. Technology Adoption in the Presence of Network Externalities[J]. Journal of Political Economy, 1986,94(4): 822 - 841.
