Funding for this research was provided by:
Council for Scientific and Industrial Research (ICT Meraka)
Text and Data Mining valid from 2019-01-30
Received: 1 August 2018
Accepted: 9 January 2019
First Online: 30 January 2019
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.