L. Moolman, S. M. Ferreira, A. Gaylard, D. Zimmerman, and G. I. Kerley, “The decline of the Knysna elephants: Pattern and hypotheses”, S. Afr. J. Sci., vol. 115, no. 3/4, Mar. 2019, doi: 10.17159/sajs.2019/4805.