Othata, Pornpon
Pochai, Nopparat http://orcid.org/0000-0002-0945-7344
Funding for this research was provided by:
Centre of Excellence in Mathematics, CHE, Thailand
Article History
Received: 30 January 2019
Accepted: 17 April 2019
First Online: 24 May 2019
Competing interests
: The authors declare that they have no competing interests.