Text and Data Mining valid from 2019-01-04
Received: 30 September 2018
Accepted: 12 December 2018
First Online: 4 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 standard of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
: For this type of study, formal consent was not required.