Text and Data Mining valid from 2019-08-01
Received: 11 May 2018
Accepted: 5 July 2019
First Online: 1 August 2019
Compliance with Ethical Standards
: The authors have no conflicts of interest to declare and no funding was received.
: A written informed consent was obtained from the parents or guardians on behalf of the minors involved, and the oral assent of the minors was also obtained.