Funding for this research was provided by:
National Research Foundation South Africa
Article History
Received: 7 May 2020
Accepted: 8 July 2020
First Online: 22 July 2020
Ethics approval and consent to participate
: No ethics approval was required for this systematic review, nor consent to participate.
: No individual-level data are included in the present study. As such, consent for publication is not needed.
: We have no financial or non-financial competing interests to declare.