Funding for this research was provided by:
Vietnam Academy of Science and Technology (KHCBVL.04/18-19)
National Foundation for Science and Technology Development (103.03-2018.306)
Text and Data Mining valid from 2019-08-29
Received: 4 June 2019
Accepted: 19 August 2019
First Online: 29 August 2019
: The authors declare no competing interests.