Text and Data Mining valid from 2018-06-21
Received: 19 December 2017
Accepted: 29 May 2018
First Online: 21 June 2018
Compliance with ethical standards
: Conflict of interest
: 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.