Nekesa, P., H. K. Maritim, J. R. Okalebo, and P. L. Woolmer. “Economic Analysis of Maize-Bean Production Using a Soil Fertility Replenishment Product (PREP-PAC) in Western Kenya”. African Crop Science Journal, vol. 7, no. 4, Apr. 1999, doi:10.4314/acsj.v7i4.27752.