E. Ndubuisi, F. Iheukwumere, and P. Etusim, “Diurnal Effects of Periodic Litter Change on Egg Production and Physical Qualities in a Deep Litter System ”, Int. J. Poult. Sci., vol. 7, no. 2, pp. 151–155, Jan. 2008, doi: 10.3923/ijps.2008.151.155.