@BOOK {COUPER:1996, title = {Use of maps for planning research farms: IITA research guide, No. 7}, author = {Couper, D. C. }, series = {IITA research guide, No. 7}, year = {1996}, month = {February}, publisher = {International Institute of Tropical Agriculture (IITA)}, address = {Ibadan, Nigeria}, note = {29p.}, }