Text and Data Mining valid from 2019-04-05
Received: 12 February 2019
Accepted: 26 March 2019
First Online: 5 April 2019
Compliance with ethical standards
: On behalf of all authors the corresponding author states that there is 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 informed consent is not required.