Funding for this research was provided by:
HCMC University of Technology and Education, Vietnam (T2018-16TÐ)
Text and Data Mining valid from 2018-07-27
Received: 7 March 2018
Accepted: 1 July 2018
First Online: 27 July 2018
Compliance with Ethical Standards
: The authors declare that they have no conflict of interest.