We have information from several sources:
Legume Species as Leaf Vegetables—Robert P. Barrett
Utility of Cowpea Foliage in a Crop Production System for Space—David L. Bubenheim, Cary A. Mitchell and Suzanne S. Nielsen
Plant Nutrient Composition Altered With Controlled Environments for Future Space Life-Support Systems—S. Suzanne Nielsen, Martha A. Belury, Kwangok P. Nickel, and Cary A. Mitchell
Cowpea—Alternative Crop Guide
Cowpea—Alternative Field Crops Manual, University of Wisconson Cooperative Extension Service, University of Minnesota Extension Service, Center for Alternative Plant & Animal Products
New Opportunities in Vigna—Richard L. Fery
Neglected Crops: 1492 from a Different Perspective—J.E. Hernándo Bermejo and J. León (eds.)
Handbook of Energy Crops—James A. Duke. 1983. unpublished.
Food and feed crops of the United States—Magness, J.R., G.M. Markle, C.C. Compton. 1971.
As hay, pasture, and soil improvement crop:
Food and feed crops of the United States—Magness, J.R., G.M. Markle, C.C. Compton. 1971.
Outside Links:
Legume—FAO/IBPGR Technical Guidelines for the Safe Movement of Legume Germplasm—Link to the publication on the International Plant Genetic Resources Institute web site