D. Franco-Jimenez and M. Beck, “Intestinal Calcium Uptake, Shell Quality and Reproductive Hormones Levels of Three Laying Hen Varieties after Prolonged Egg Production”, Int. J. Poult. Sci., vol. 4, no. 8, pp. 518–522, Jul. 2005, doi: 10.3923/ijps.2005.518.522.