Lindén, H., T. Nygård, and M. Wikman. “On the Eggshell Thickness and Reproduction of the Peregrine Falcon Falco Peregrinus in Finland”. Ornis Fennica, vol. 61, no. 4, Dec. 1984, pp. 116–120, https://ornisfennica.journal.fi/article/view/133159.