@BOOK {COUPER:1993a, title = {Consevation des sols: utilization des banquettes a double courbure: Guide de recherche de l'Iita, No. 6}, author = {Couper, D. C. }, series = {Guide de recherche de l'Iita, No. 6}, year = {1993}, month = {February}, publisher = {International Institute of Tropical Agriculture (IITA)}, address = {Ibadan, Nigeria}, note = {25p.}, }