Koskimies, J. “Seasonal, Geographical and Yearly Trends in the Weight of Capercaillie (Tetrao Urogallus) and Blackgame (Lyrurus Tetrix) in Finland”. Ornis Fennica, vol. 35, no. 1, Mar. 1958, pp. 1–18, https://ornisfennica.journal.fi/article/view/132617.