Sayed, R. K., K. E. Abdalla, A. K. Ahmed, and A. M. Saleh. “Morphological Studies on the Upper Beak of Turkey (Meleagris Gallopavo)”. Journal of Advanced Veterinary Research, vol. 4, no. 4, Oct. 2014, pp. 154-60, https://advetresearch.com/index.php/AVR/article/view/92.