HAAPANEN, Antti; HAUTALA, Hannu. Bimodality of spring migration of the Whooper Swan Cygnus cygnus in Finland. Wildfowl, [S. l.], p. 195–200, 2013. Disponível em: https://tidsskrift.dk/Wildfowl/article/view/154974. Acesso em: 17 dec. 2025.