“The Result of Quantity and Placement Distances of Inorganic 15-15-15 Fertilizer in Improving Soil Fertility and Yield of Maize in a Tropical Rain Forest Zone of Nigeria”. International Journal of Manures and Fertilizers, vol. 1, no. 1, May 2012, pp. 135-43, https://ijpp.org/journal/index.php/ijmf/article/view/268.