NWAOGUALA, N. C., 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”. Notulae Scientia Biologicae, vol. 10, no. 4, Dec. 2018, pp. 516-21, doi:10.15835/nsb10410393.