@BOOK {STOORVOGEL:1991, title = {The identification of agro-ecological zones for cassava in Africa with particular emphasis on soils: COSCA working paper, No. 5}, author = {Stoorvogel, J. and Fresco, L. }, series = {COSCA working paper}, year = {1991}, number = {5}, publisher = {International Institute of Tropical Agriculture (IITA)}, address = {Ibadan, Nigeria}, note = {RTB; Root and Tuber; Cassava.; 5p.}, }