KIRBY, Jeff S; REES, Eileen C; MERNE, Oscar J; GARDARSSON, Arnthor. International census of Whooper Swans Cygnus cygnus in Britain, Ireland and Iceland: January 1991. Wildfowl, [S. l.], p. 20–26, 1992. Disponível em: https://tidsskrift.dk/Wildfowl/article/view/155372. Acesso em: 17 dec. 2025.