1. School of Mathematical Sciences, Tongji University, Shanghai 200092, People's Republic of China
2. Department of Mathematics, Ryerson University, Toronto, ON, Canada
3. Business School, Chengdu University, Chengdu 610106, People's Republic of China
4. School of Financial Technology, Shanghai Lixin University of Accounting and Finance, Shanghai 201209, People's Republic of China
5. Business School, Sun Yat-Sen University, Guangzhou 510275, People's Republic of China
6. Center for Financial Engineering, Soochow University, Suzhou 215008, People's Republic of China