Jansen van Rensburg, H.G. (Hester Getruida); Claassens, A.S. (Andries Stephanus), 1943-; Beukes, D.J.; Weepener, H.L.; Beukes, P.J.(South African Society of Crop Production/ Soil Science Society of South Africa/ Southern African Weed Science Society/ Southern African Society for Horticultural Sciences, 2009)