Text and Data Mining valid from 2019-03-13
Received: 11 February 2019
Accepted: 20 February 2019
First Online: 13 March 2019
Compliance with ethical standards
: The authors declare that the work described has not been published before; that it is not under consideration for publication anywhere else; that its publication has been approved by all co-authors; that there is no conflict of interest regarding the publication of this article.