Doyer, O.T.; D'Haese, M.F.C. (Marijke); Kirsten, Johann F.; Van Rooyen, C.J. (Cornelius Johannes)(Agricultural Economics Association of South Africa, 2007-12)
Sartorius, Kurt; Kirsten, Johann F.(Independent Regulatory Board for Auditors (IRBA), SA Institute of Chartered Accountants (SAICA) & SA Association of Accountants (SAAA), 2004-06)