Manorod, Songabsorn
Rattanakul, Chontita http://orcid.org/0000-0002-2362-5885
Funding for this research was provided by:
Centre of Excellence in Mathematics, Thailland
Article History
Received: 31 January 2019
Accepted: 25 June 2019
First Online: 4 July 2019
Competing interests
: The authors declare that they have no competing interests.