Shafey, T.M., M.M. Ghannam, H.A. Al-Batshan, and M.S. Al-Ayed. 2004. “Effect of Pigment Intensity and Region of Eggshell on the Spectral Transmission of Light That Passes the Eggshell of Chickens”. International Journal of Poultry Science 3 (3): 228–233. https://doi.org/10.3923/ijps.2004.228.233.