Ahmed, F. A. “Method of Bill Trimming Can Affect the Behaviour, Performance, and Welfare of Mule Duck: Bill Trimming and Mule Duck Behaviour and Welfare”. PSM Veterinary Research, vol. 7, no. 1, Apr. 2022, pp. 11-19, https://psmjournals.org/index.php/vetres/article/view/629.