Article History
Received: 8 July 2018
Accepted: 8 February 2019
First Online: 28 February 2019
Compliance with ethical guidelines
:
: E.K. Appiah-Dwomoh, S. Müller and F. Mayer declare that they have no competing interests.
: The institution’s ethics committee gave ethical approval and the study was performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments. Participants and their parents or guardians gave written informed consent before data collection.