North, Ernest J.; Millard, Sollie M.(Innovatio Publishers (Germany), Media Tenor (South Africa) and the Institute for Media Analysis in South Africa (Imasa), 2003)
Gaigher, Estelle; Rogan, John M.; Braun, Max Willi Hermann(Southern African Association for Research in Mathematics, Science and Technology Education, 2006)
Stevens, K.B.; Spickett, Arthur M.; Vosloo, Wilna; Pfeiffer, Dirk U.; Dyason, Edwin; Du Plessis, B.(Agricultural Research Council, ARC-OVI and the University of Pretoria, 2007-06)
Potgieter, Marietjie; Rogan, John M.; Howie, Sarah J.(Southern African Association for Research in Mathematics, Science and Technology Education, 2005)