J. C. Nwite, P. O. Okereke, O. C. Olejeme & C. I. Keke. Evaluation of Varietal Effect and Different Manure Sources on the Soil Chemical Properties, Growth and Yield of Sweet Potato (lpomea Batatas L.) in Ishiagu, Southeastern Nigeria. Arch. Curr. Res. Int. 2015, 3, 1–9.