Funding for this research was provided by:
Text and Data Mining valid from 2019-08-23
Received: 5 November 2018
Accepted: 12 August 2019
First Online: 23 August 2019
Ethics approval and consent to participate
: The study was approved by the ethics council of Hanoi University of Public Health (decision number 240/2015/YTCC-HD in 2015). Written consent form was signed and given by all participants.
: The written consent form that was signed by all participants included consent to publish their information as aggregated information (i.e., no personal information to identify persons should be published).
: The authors declare that they have no competing interests.