Akpa, G.N., et al. “The Relationships Between Laying Age and Repeatability of Egg Quality Traits in Japanese Quails (Coturnix Coturnix japonica()”. International Journal of Poultry Science, vol. 7, no. 6, May 2008, pp. 555–559, https://doi.org/10.3923/ijps.2008.555.559.