O. Järvinen and R. A. Väisänen, “Species diversity of Finnish birds, I: Zoogeographical zonation based on land birds”, Ornis Fenn, vol. 50, no. 3–4, pp. 93–125, Dec. 1973, Accessed: Jan. 09, 2026. [Online]. Available: https://ornisfennica.journal.fi/article/view/132855