@ARTICLE {MANYONG:1997g, title = {Measurement of the sustainability of African smallholder farming systems: case study of a systems approach*}, author = {Manyong, V. and Degand, J. }, journal = {IITA Research}, year = {1997}, month = {September}, number = {14/15}, pages = {1--6}, issn = {1115-3067}, }