Text and Data Mining valid from 2019-09-11
Received: 22 March 2019
Accepted: 27 August 2019
First Online: 11 September 2019
Ethics approval and consent to participate
: No ethical clearance was required since the data used in the study is secondary and available in the public domain. No prior consent was needed.
: Not applicable.
: The authors declare that they have no competing interests.