1. School of Economics, Sichuan University, #24, Yihuannan Road, Chengdu 610065, China
2. Sichuan Key Laboratory of Science & Technology, Finance and Mathematical Finance, #24, Yihuannan Road, Chengdu 610065, China
3. College of Economics, Sichuan Agricultural University, #211, Huimin Road, Wenjiang District, Chengdu 611130, China