Funding for this research was provided by:
National Research Foundation (82769)
Text and Data Mining valid from 2018-07-11
Received: 1 December 2017
Accepted: 5 June 2018
First Online: 11 July 2018
Ethics approval and consent to participate
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.