Cordero, P. J. “Phenotypes of Juvenile Offspring of a Mixed Pair Consisting of a Male House Sparrow and a Female Tree Sparrow Passer Spp”. Ornis Fennica 67, no. 2 (July 1, 1990): 52–56. Accessed November 22, 2024. https://ornisfennica.journal.fi/article/view/133300.