1. School of Mathematics and Statistics, Chongqing Technology and Business University, Chongqing, People's Republic of China
2. Chongqing Key Laboratory of Social Economy and Applied Statistics, Chongqing, People's Republic of China
3. College of Mathematics, Sichuan University, Chengdu, People's Republic of China
4. College of Mathematics, People Liberate Army Engineering University, Shijiazhuang, People's Republic of China