Häkkinen, I., M. Jokinen, and J. Tast. “The Winter Breeding of the Feral Pigeon Columba Livia Domestica at Tampere in 1972/1973”. Ornis Fennica, vol. 50, no. 2, July 1973, pp. 83–88, https://ornisfennica.journal.fi/article/view/132853.