Text and Data Mining valid from 2019-05-17
Received: 17 February 2019
Accepted: 6 May 2019
First Online: 17 May 2019
Compliance with ethical standards
: The authors declare that they have no conflicts 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.