Funding for this research was provided by:
Ministry of Science and Technology, Taiwan (MOST-104-2115-M-009-014-MY3, MOST-104-2115-M-009-012-MY2)
National Chiao Tung University (NCTU Taiwan Elite Internship Program)
Mathematics Division, National Center for Theoretical Sciences
Article History
Received: 6 October 2017
Revised: 22 January 2018
Accepted: 30 January 2018
First Online: 9 February 2018