Funding for this research was provided by:
National Natural Science Foundation of China (11601155, 11571363)
National Natural Science Foundation of China (11431005)
Recruitment Program of Global Experts in China (18dz2271000)
National Science Foundation (DMS-1411476, DMS-1210400)
National Science Foundation (DMS-1714487)
Article History
Received: 29 May 2018
Revised: 30 November 2018
First Online: 2 January 2019