Text and Data Mining valid from 2019-07-15
Received: 6 January 2019
Accepted: 21 May 2019
First Online: 15 July 2019
Ethics approval and consent to participate
: As a document-based study, ethical approval was not required, and issues of consent to participate did not arise.
: No consent is required for publication, other than from the authors.
: The authors declare that they have no competing interests.