I. . Gideon, A. . Ogbonna, and E. . Nzegbule, “Soil Physico-Chemical Properties in Three Land Use Systems (Theobroma Cacao, Gmelina Arborea and Secondary Forest) in Umuahia North of Abia State, Nigeria”, Ca J Agri Crop, vol. 1, no. 1, pp. 19–29, Jun. 2016.