Text and Data Mining valid from 2019-04-15
Received: 22 January 2019
Revised: 14 March 2019
Accepted: 21 March 2019
First Online: 15 April 2019
Compliance with ethical standards
: There was no research involving human participants and/or animals. The work has been submitted with the consent of all authors.
: The authors declare that they have no conflicts of interest.