Van Heerden, Cornelius Hendrik, 1957-; Kotze, Theuns G.; Bruwer, Johan(Southern African Alliance for Sport Science, Physical Education and Recreation, 2004)
Douglas, Anneli; Mostert, P.G. (Pierre); Slabbert, Liandi Magdalena(Department of Recreation, Park, and Tourism Sciences at Texas AandM University, 2019)