Text and Data Mining valid from 2019-02-04
Received: 28 October 2018
Accepted: 28 January 2019
First Online: 4 February 2019
Compliance with ethical standards
: The authors of this study declare no conflict of interest. The authors of this study declare no financial support.
: The article is in accordance with ethical standards.
: This study does not contain any study with human participants performed by any of the authors.