On the spring migration of the Whooper Swan (Cygnus cygnus) in the Helsinki region in the years 1950–61

Jahnukainen, M. (1963). On the spring migration of the Whooper Swan (Cygnus cygnus) in the Helsinki region in the years 1950–61. Ornis Fennica, 40(1), 1–12. Noudettu osoitteesta https://ornisfennica.journal.fi/article/view/132679