Kampe-Persson, Hakon. “Variation in Bill Colour Among Greylag Geese Anser Anser Breeding in South-West Scania”. Ornis Svecica 13, no. 2–3 (July 1, 2003): 63–66. Accessed November 22, 2024. https://journals.lub.lu.se/os/article/view/22808.