Text and Data Mining valid from 2018-07-18
Received: 4 June 2018
Accepted: 11 July 2018
First Online: 18 July 2018
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.