Wiktander, U., I. N. Nilsson, S. G. Nilsson, O. Olsson, B. Pettersson, and A. Stagen. “Occurrence of the Lesser Spotted Woodpecker Dendrocopos Minor in Relation to Area of Deciduous Forest”. Ornis Fennica, vol. 69, no. 3, Sept. 1992, pp. 113–118, https://ornisfennica.journal.fi/article/view/133347.