BORGSTRÖM, E.; SCHÜTT, L. A long term study (1938—2004) of arrival dates of migratory birds in middle Värmland. Ornis Svecica, Lund, Sweden, v. 16, n. 3, p. 95–111, 2006. DOI: 10.34080/os.v16.22717. Disponível em: https://journals.lub.lu.se/os/article/view/22717. Acesso em: 6 jul. 2022.