NIEMELÄ, P.; SALO, J.; LAAKSONEN, H. Frederick II of Hohenstaufen, Bergmann`s rule and Aristotelian typology. Ornis Fennica, [S. l.], v. 68, n. 1, p. 33–35, 1991. Disponível em: https://ornisfennica.journal.fi/article/view/133313. Acesso em: 16 may. 2024.