1. Adachi, J., and Hasegawa, M. (1992).MOLPHY: Programs for Molecular Phylogenetics, I. PROTML: Maximum Likelihood Inference of Protein Phylogeny, Institute of Statistical Mathematics, Tokyo.
2. Àrnason, U., and Widegren, B. (1986). Pinniped phylogeny enlightened by molecular hybridizations using highly repetitive DNA,Mol. Biol. Evol. 3, 356–365.
3. Àrnason, U., Gullberg, A., Johnsson, E., and Ledje, C. (1993). The nucleotide sequence of the mitochondrial DNA molecule of the grey seal,Halichoerus grypus, and a comparison with mitochondrial sequences of other true seals,J. Mol. Evol. 37, 323–330.
4. Àrnason, U., Bodin, K., Gullberg, A., Ledje, C., and Mouchaty, S. (1995). A molecular view of pinniped relationships with particular emphasis on the true seals,J. Mol. Evol. 40, 78–85.
5. Burns, J. J., and Fay, F. H. (1970). Comparative morphology of the skull of the ribbon seal,Histriophoca fasciata, with remarks on systematics of Phocidae,J. Zool. 161, 363–394.