@BOOK {DVORAK:1996, title = {Exploratory surveys in research planning: IITA research guide, No. 28}, author = {Dvorak, K. A. and Izac, A. M. N. }, series = {IITA research guide, No. 28}, year = {1996}, month = {October}, publisher = {International Instute of Tropical Agriculture (IITA)}, address = {Ibadan, Nigeria}, note = {25p.}, }