@BOOK {COUPER:1995, title = {Building and maintenance of roads on agricultural research farms: IITA research guide, No. 20}, author = {Couper, D. C. }, series = {IITA research guide, No. 20}, year = {1995}, month = {September}, publisher = {International Institute of Tropical Agriculture (IITA)}, address = {Ibadan, Nigeria}, note = {20p.}, }