Text and Data Mining valid from 2018-05-11
Received: 11 January 2018
Accepted: 2 April 2018
First Online: 11 May 2018
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: All study protocols were approved by Hanoi Medical University Ethical Committee and have therefore been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.