Text and Data Mining valid from 2019-03-05
Received: 7 February 2018
Accepted: 26 February 2019
First Online: 5 March 2019
Ethics approval and consent to participate
: The study was approved by the medical ethics committee of the University of Oldenburg (reference no. 2017–032). All participants had to give written informed consent. Parental consent was obtained for study participants under 18 years of age.
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.