McCracken, Jennifer A., and Jules N. Pretty. (1988) 1988. Glossary of Selected Terms in Sustainable Agriculture. Gatekeeper Series No. SA6. London; Washington, DC: International Institute for Environment and Development, Sustainable Agriculture Programme. http://www.worldcat.org/oclc/19531919.
food crops
Bourke, R. Michael. (1985) 1985. “Food, Coffee and Casuarina: An Agroforestry System from the Papua New Guinea Highlands”. Agroforestry Systems 2 (4): 273-79. doi:10.1007/BF00147038.
Oladokun, M. A. O. (1990) 1990. “Tree Crop Based Agroforestry in Nigeria: A Checklist of Crops Intercropped With Cocoa”. Agroforestry Systems 11 (3): 227-41. doi:10.1007/BF00045901.