Nilsson, Leif, Ove Andersson, Rolf Gustafsson, and Mikael Svensson. “Increase and Changes in Distribution of Breeding Whooper Swans Cygnus Cygnus in Northern Sweden from 1972-75 to 1997”. Wildfowl (January 1, 1998): 6–17. Accessed December 17, 2025. https://tidsskrift.dk/Wildfowl/article/view/154602.