Makoi, J.H. and Ndakidemi, P.A. 2010. Effect of plant densities and cropping systems on yield components of cowpea (<i>Vigna unguiculata</i> L. Walp.) genotypes and sorghum (<i>Sorghum bicolor </i>L. Moench.). Journal of Tropical Agriculture. 48, 2 (Dec. 2010), 28–33.