Text and Data Mining valid from 2019-02-09
Received: 6 August 2018
Revised: 21 January 2019
Accepted: 27 January 2019
First Online: 9 February 2019
Compliance with ethical standards
: Jungpil Shin declares that he has no conflict of interest. Cheol Min Kim and MA Rahim also declares that they have no conflict of interest.