1. Department of Mathematics and Statistics, Georgetown University, Washington, DC, USA
2. Graduate Institute of Business Administration, College of Management, Fu Jen Catholic University, New Taipei City, Taiwan
3. Hubei Key Laboratory of Applied Mathematics, Faculty of Mathematics and Statistics, Hubei University, Wuhan, People's Republic of China
4. Laboratory of Mathematics and Complex Systems (Ministry of Education of China), School of Mathematical Sciences, Beijing Normal University, Beijing, People's Republic of China