This manual was coordinated by W.A. Geering. The authors were G. Bruckner, A.I. Donaldson, A. James, J. McDermott, T. Leyland, R.S. Morris, A. Permin, M.M. Rweyemamu, D. Ward and R. Webb. The FAO (AGA) collaborators were Y. Cheneau, J. Hansen, J. Otte, R. Paskin, P. Roeder and J. Slingenbergh. The various contributions by the many people and institutions concerned with this manual are gratefully acknowledged. Editorial and production were coordinated by David Nyakahuma (AGA).