Text and Data Mining valid from 2020-01-10
Received: 11 September 2019
Accepted: 1 January 2020
First Online: 10 January 2020
Ethics approval and consent to participate
: This study was performed in accordance with the ethical standards of the institutional and/or national research committee and the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. It was approved by the Ethics Committee of the Faculty of Medicine, Chiang Mai University (no. 202-2013). All of the participants gave their written informed consent prior to entering the study.
: Not applicable
: The authors declare that they have no competing interests.