N. C. NWAOGUALA and K. E. LAW-OGBOMO, “Comparative Effect of Poultry and Swine Manures on the Performance of White Guinea Yam (Dioscorea rotundata Poir) in an Ultisols Environment”, Not Sci Biol, vol. 10, no. 4, pp. 516–521, Dec. 2018.