JAHNUKAINEN, M. On the spring migration of the Whooper Swan (Cygnus cygnus) in the Helsinki region in the years 1950–61. Ornis Fennica, [S. l.], v. 40, n. 1, p. 1–12, 1963. Disponível em: https://ornisfennica.journal.fi/article/view/132679. Acesso em: 23 nov. 2024.