na INLIS000000000005867 0010-1021000701 Raising and sustaining Productivity of Smallholder Farming Systems in the Tropics A. Handbook of Sustainable Agricultural Development Willem C. Beets Alkmaar Holland: Ag Be Publishing 1990 XVI, 738p; ill; 27 cm Ref. 631. 58 Ref. 631. 58 FARMING SYSTEMS TROPICS AGRICULTURAL DEVELOPMENT. 5091