Esparza, B., A. Martínez-Abraín, S. Merino, and D. Oro. “Immunocompetence and the Prevalence of Haematozoan Parasites in Two Long-Lived Seabirds”. Ornis Fennica, vol. 81, no. 1, Mar. 2004, pp. 40–46, https://ornisfennica.journal.fi/article/view/133611.