Williams, Melissa A., et al. “Effect of Early Post-Hatch Feeding on Yolk Sac Disappearance, Feed Intake and Weight of Newly Hatched Mule Ducklings in a Tropical Environment”. Pakistan Journal of Nutrition, vol. 19, no. 2, Jan. 2020, pp. 74–79, https://doi.org/10.3923/pjn.2020.74.79.