OSTAPENKO, V A. Migration of Bewick’s Swans Cygnus bewickii and Whooper Swans C. cygnus wintering in Japan through Sakhalin Island and adjacent territories, USSR. Wildfowl, [S. l.], p. 224–226, 2013. Disponível em: https://tidsskrift.dk/Wildfowl/article/view/154979. Acesso em: 17 dec. 2025.