Text and Data Mining valid from 2019-07-01
Received: 12 May 2019
Accepted: 24 June 2019
First Online: 1 July 2019
Availability of data and materials
: The analysed data sets generated during the study are available from the corresponding author on reasonable request.
: 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.
: Not applicable.
: The authors declare they have no competing interests.