(en) Thomas Cavalier-Smith, « A revised six-kingdom system of life », Biological reviews, vol. 73, no 3, , p. 203-266 (DOI10.1111/j.1469-185X.1998.tb00030.x).
(en) Alysha M. Heimberg, Richard Cowper-Sal·lari, Marie Sémon, Philip C. J. Donoghue et Kevin J. Peterson, « MicroRNAs reveal the interrelationships of hagfish, lampreys and gnathostomes and the nature of the ancestral vertebrate », Proceedings of the National Academy of Sciences, vol. 107, no 45, , p. 19379-19383 (DOI10.1073/pnas.1010350107).