Iqbal, K http://orcid.org/0000-0002-3312-4259
Schwingshackl, L
Gottschald, M http://orcid.org/0000-0002-1716-2132
Knüppel, S
Stelmach-Mardas, M
Aleksandrova, K
Boeing, H
Article History
Received: 12 January 2017
Revised: 10 May 2017
Accepted: 1 June 2017
First Online: 26 July 2017
Competing interests
: The authors declare no conflict of interest.