Balfour, F.M. (1878)
A monograph on the Development of Elasmobranch Fishes. London, 287 pp

Balfour, F.M. (1875)
On the Development of the Spinal Nerves in Elasmobranch Fishes. Proceedings of the Royal Society of London (1854–1905), 24(1), 124–136
DOI: 10.1098/rspl.1875.0014