Zheng, Hongya, Baoming Li, Qin Tong, Gang Chen, and Xuanyang Li. 2019. “Modification of Perchery System: Preference for Ramps Rather Than Ladders During Early Adaptation Period for Cage-Reared Pullets”. International Journal of Agricultural and Biological Engineering 12 (4):34-42. https://doi.org/10.25165/ijabe.v12i4.4030.