2001 · W. A.J. Berry, E. B. Birch, et al. · Conservation agriculture, a worldwide challenge. First World Congress on conservation agriculture, Madrid, Spain, 1-5 October, 2001. Volume 2: offered contributions.
1993 · J. B. Mallett, B.S.E. Clemence, et al. · Proceedings of the Annual Scientific Conference of the SADCC-Land and Water Management Research Programme