Marpaung, David https://orcid.org/0000-0002-5434-7195
Yao, Jianping https://orcid.org/0000-0002-6877-7057
Capmany, José
Article History
Received: 31 May 2018
Accepted: 5 October 2018
First Online: 21 January 2019
Competing interests
: The authors declare no competing interests.