Orvig, T. (1985)
Histologic studies of ostracoderms, placoderms and fossil elasmobranchs. 5. Ptyctodontid tooth plates and their bearing on holocephalan ancestry: the condition of chimaerids.
Zoologica Scripta, 14(1), 55–79 DOI: 10.1111/j.1463-6409.1985.tb00178.x