Kombiok, J M, E Y Safo, and C Quansah. “Effects of Tillage and Cropping Systems on Yield and Nitrogen Fixation of Cowpea Intercropped With Maize in Northern Guinea Savanna Zone of Ghana”. Ghana Journal of Agricultural Science 39, no. 1 (September 26, 2007): 61–76. Accessed October 10, 2026. https://www.ajol.info/index.php/gjas/article/view/2127.