Text and Data Mining valid from 2018-08-17
Received: 2 November 2017
Accepted: 9 August 2018
First Online: 17 August 2018
Compliance with ethical standards
: The authors declare that they have no conflicts of interest.
: This article does not refer to any studies involving human participants or animals performed by the authors.
: For this type of study, formal consent is not required.