Guo, Hailong http://orcid.org/0000-0001-7621-2315
Yang, Xu
Funding for this research was provided by:
Division of Mathematical Sciences (DMS-1418936, DMS-1107291)
Article History
Received: 7 March 2016
Revised: 16 August 2016
Accepted: 20 October 2016
First Online: 25 October 2016