Text and Data Mining valid from 2019-03-12
Received: 10 October 2018
Accepted: 21 February 2019
First Online: 12 March 2019
Compliance with ethical standards
: The authors declare that they have no direct or indirect conflict of interest.
: This is the original work of the authors. The work described has not been submitted elsewhere for publication, in whole or in part, and all authors listed carried out the data analysis and manuscript writing. This article does not contain any studies with human participants or animals performed by any of the authors. Moreover, all authors read and approved the final manuscript.