Geremew, Eticha Birdo; Steyn, Joachim Marthinus; Annandale, John George(South African Society of Crop Production/ Soil Science Society of South Africa/ Southern African Weed Science Society/ Southern African Society for Horticultural Sciences, 2008)
Alemayehu, Y.A.; Steyn, Joachim Marthinus; Annandale, John George(South African Society of Crop Production/ Soil Science Society of South Africa/ South African Weed Science Society/ South African Society for Horticultural Sciences, 2009-07)