Funding for this research was provided by:
National Natural Science Foundation of China (NSFC 11471031)
National Natural Science Foundation of China (NSFC 91430216)
National Natural Science Foundation of China (NSAF U1530401)
National Science Foundation (DMS-1419040)
National Science Foundation (DMS-1521555)
Article History
Received: 16 March 2018
Accepted: 21 June 2019
First Online: 4 July 2019