RUSSELL, D. E.; MARTELL, A. M. Winter ecology of the Porcupine caribou herd, Yukon: Part III, Role of day length in determining activity pattern and estimating percent lying. Rangifer, [S. l.], v. 6, n. 2, p. 253–259, 1986. DOI: 10.7557/2.6.2.656. Disponível em: https://septentrio.uit.no/index.php/rangifer/article/view/656. Acesso em: 26 oct. 2021.