Per Erik Ahlberg, “A re-examination of sarcopterygian interrelationships, with special reference to the Porolepiformes,” Zoological Journal of the Linnean Society, Volume 103, Issue 3, Linnean Society of London, 1991, Pages 241–287, https://doi.org/10.1111/j.1096-3642.1991.tb00905.x.