Durand, J. 2004. “The Discovery of an Engraving Near Mapungubwe That Could Have Been Used As an Abacus”. Suid-Afrikaans Tydskrif Vir Natuurwetenskap En Tegnologie / <i>South African Journal of Science and Technology</I&gt; 23 (3), 46-51. https://doi.org/10.4102/satnt.v23i3.192.