Cuadrago, M., and D. Hasselquist. “Age-Related Difference in Return Rate of Willow Warblers Phylloscopus Trochilus at Two Breeding Sites in Sweden”. Ornis Fennica 71, no. 4 (December 31, 1994): 137–143. Accessed May 18, 2024. https://ornisfennica.journal.fi/article/view/133404.