Jansson, G., and L. Saari. “Suitable Habitat Distribution for the Long-Tailed Tit (Aegithalos Caudatus) As Indicated by the Frequency of Occurrence-a Longterm Study”. Ornis Fennica, vol. 76, no. 3, Sept. 1999, pp. 115–122, https://ornisfennica.journal.fi/article/view/133506.