Text and Data Mining valid from 2019-04-10
Received: 23 January 2019
Accepted: 1 April 2019
First Online: 10 April 2019
Compliance with ethical standards
: The author declares that he has no conflict of interest.
: This article does not contain any studies with human participants or animals performed by any of the authors.
: For this type of study formal consent is not required.