Text and Data Mining valid from 2018-01-29
Received: 21 August 2017
Accepted: 4 January 2018
First Online: 29 January 2018
Compliance with ethical standards
: The authors declare that they have no conflict of interest. This manuscript does not contain any studies with human participants or animals performed by any of the authors. Authors have carefully checked the “Instructions for Authors” and certify that the manuscript complies with the Ethical Rules applicable for this journal.