Funding for this research was provided by:
NSFC (11671098, 11331004)
NSFC (91630309)
111 Project (B08018)
NSF (DMS-1418689)
Shanghai University of Finance and Economics (2017110715)
Article History
Received: 2 November 2017
Revised: 1 February 2018
Accepted: 5 March 2018
First Online: 10 March 2018