Curtis B., Roberts K. S., Griffin M., Bethune S., Hay C. J. & Kolberg H. 1998. "Species richness and conservation of Namibian freshwater macro-invertebrates, fish and amphibians". Biodiversity and Conservation7(4): 447-466. doi:10.1023/A:1008871410919, PDF.
Curtis B., Roberts K. S., Griffin M., Bethune S., Hay C. J. & Kolberg H. 1998. "Species richness and conservation of Namibian freshwater macro-invertebrates, fish and amphibians". Biodiversity and Conservation7(4): 447-466. doi:10.1023/A:1008871410919, PDF.