Text and Data Mining valid from 2018-11-14
Received: 23 May 2018
Accepted: 31 October 2018
First Online: 14 November 2018
Ethics approval and consent to participate
: We analyzed publicly available data as such no formal ethical review is required.
: Not applicable because there are no individual details, images and videos in this study.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.