Funding for this research was provided by:
Deutsche Forschungsgemeinschaft (SCHN 415/8-1)
Text and Data Mining valid from 2018-10-23
First Online: 23 October 2018
Compliance with Ethical Standards
: The authors declare no conflict of interest.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
: All parents provided written informed consent prior to participating in the present study.