Delabre, Christiane (2002). «Complete Mitochondrial DNA of the Hagfish, Eptatretus burgeri: The Comparative Analysis of Mitochondrial DNA Sequences Strongly Supports the Cyclostome Monophyly». Molecular Phylogenetics and Evolution22 (2): 184-192. PMID11820840. doi:10.1006/mpev.2001.1045.
Stock, David; Whitt GS (7 de agosto de 1992). «Evidence from 18S ribosomal RNA sequences that lampreys and hagfishes form a natural group». Science257 (5071): 787-9. PMID1496398. doi:10.1126/science.1496398.
Delabre, Christiane (2002). «Complete Mitochondrial DNA of the Hagfish, Eptatretus burgeri: The Comparative Analysis of Mitochondrial DNA Sequences Strongly Supports the Cyclostome Monophyly». Molecular Phylogenetics and Evolution22 (2): 184-192. PMID11820840. doi:10.1006/mpev.2001.1045.
Stock, David; Whitt GS (7 de agosto de 1992). «Evidence from 18S ribosomal RNA sequences that lampreys and hagfishes form a natural group». Science257 (5071): 787-9. PMID1496398. doi:10.1126/science.1496398.