@BOOK {HORTON:1997, title = {Tips for planning formal farm surveys in developing countries: IITA research guide, No. 31}, author = {Horton, D. }, series = {IITA research guide, No. 31}, year = {1997}, month = {July}, publisher = {International Institute of Tropical Agriculture (IITA)}, address = {Ibadan, Nigeria}, isbn = {978-131-112-6}, note = {37p.}, }