Funding for this research was provided by:
Text and Data Mining valid from 2018-01-27
Received: 6 July 2017
Accepted: 4 January 2018
First Online: 27 January 2018
Compliance with ethical standards
: The authors declare that they have no conflict of interests.
: Ethical consideration of this study was sent for approval by the Chiang Mai Public Health Office Institutional Review Board, Ministry of Public Health, Thailand. All the respondents signed an informed consent form.