4Cha M, Haddadi H, Benevenuto F, et al. Measuring user influence in Twitter: The million follower fallacy[J]. IO- WSM, 2010:10-17.
5Castillo-Merino D, SerradelI-L6pez E. An analysis of the determinants of students' performance in e-learning[J]. Computers in Human Behavior, 2014(30): 476-484.
6Bayraktar E, Tatoglu E, Turkyilmaz A, et al. Measuring the efficiency of customer satisfaction and loyalty for mobile phone brands with DEA[J]. Expert Systems with Applications, 2012, 39( 1): 99-106.
7Andersen P, Petersen N C. A procedure for ranking efficient units in data envelopment analysis[J]. Management Sci- ence, 1993, 39(10): 1261-1264.