BOWLER, Jonathan M; BUTLER, Linda; REES, Eileen C. Bewick’s and Whooper Swans Cygnus columbianus bewickii and C. cygnus: the 1992-93 season. Wildfowl, [S. l.], p. 191–199, 1993. Disponível em: https://tidsskrift.dk/Wildfowl/article/view/154692. Acesso em: 16 dec. 2025.