[1] [1] LIU X Y, PENG H Q, BAI Y, et al. Tourism flows prediction based on an improved grey GM(1, 1) model［J］. Procedia-Social and Behavioral Sciences, 2014, 138: 767-775.

[3] [3] LI M S, WEN Z K. Research on logistics volume forecast based on improved GM (1, 1) model［J］. Energy Procedia, 2011, 13：8521-8526.

[7] [7] YAO T X, LIU S F, XIE N M. On the properties of small sample of GM(1, 1)model［J］. Applied Mathematical Modelling, 2008, 33(4): 1894-1903.