Text and Data Mining valid from 2019-02-01
Received: 12 July 2018
Revised: 11 December 2018
Accepted: 27 January 2019
First Online: 1 February 2019
Compliance with ethical standards
: The author declares that no conflict of interest exists.
: This article does not contain any studies with human participants or animals performed by the author.
: No individual participants were included in the study so there are no subjects for informed consent requirements.