Funding for this research was provided by:
Text and Data Mining valid from 2019-01-24
Received: 27 November 2018
Accepted: 29 December 2018
First Online: 24 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 institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
: Verbal informed consent was obtained from all individual participants included in the study.