KONDRATIEV, A Ya. The distribution and status of Bewick’s Swans Cygnus bewickii, Tundra Swans C. columbianus and Whooper Swans C. cygnus in the "Extreme Northeast" of the USSR. Wildfowl, [S. l.], p. 56–61, 2013. Disponível em: https://tidsskrift.dk/Wildfowl/article/view/155010. Acesso em: 16 dec. 2025.