Text and Data Mining valid from 2019-05-17
Received: 16 January 2019
Revised: 31 March 2019
Accepted: 6 May 2019
First Online: 17 May 2019
Compliance with ethical standards
: The authors declare that they have 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.
: The nature of this article did not require informed consent