E Rava, E Chirwa, P Allison, M van Niekerk, and MP Augustyn, “The use of exogenous microbial species to enhance the performance of a hybrid fixed-film bioreactor treating coal gasification wastewater to meet discharge requirements”, WSA, vol. 42, no. 3 July, Jul. 2016, doi: 10.4314/wsa.v42i3.14.