Text and Data Mining valid from 2019-03-15
Received: 26 January 2019
Revised: 7 March 2019
Accepted: 8 March 2019
First Online: 15 March 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. For this type of study, formal consent is not required.