Text and Data Mining valid from 2019-01-30
Received: 15 September 2018
Revised: 9 January 2019
Accepted: 17 January 2019
First Online: 30 January 2019
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the Recommendations of the Commission on Professional Self-Regulation in Science (DFG: Deutsche Forschungsgemeinschaft) [CitationRef removed] and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
: Informed consent was obtained from all individual participants included in the study.