Ferguson, S. J. (2001). "Keilin's Cytochromes: How Bacteria Use Them, Vary Them and Make Them". Biochemical Society Transactions. 29 (6): 629–640. doi:10.1042/bst0290629.
Hartree, E. F. (1 October 1973). "The discovery of cytochrome". Biochemical Education. 1 (4): 69–71. doi:10.1016/0307-4412(73)90074-5.