Ndubuisi, E.C., F.C. Iheukwumere, and P.E. Etusim. 2008. “Diurnal Effects of Periodic Litter Change on Egg Production and Physical Qualities in a Deep Litter System ”. International Journal of Poultry Science 7 (2): 151–155. https://doi.org/10.3923/ijps.2008.151.155.