Text and Data Mining valid from 2019-02-06
Received: 10 September 2018
Accepted: 14 November 2018
First Online: 6 February 2019
Ethics approval and consent to participate
: For this kind of study, no formal IRB approval is needed.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.