↑ ITIS (Integrated Taxonomic Information System). www.itis.gov
↑ Boulenger, G.A. 1893. Catalogue of the Snakes in the British Museum (Natural History). Volume I., Containing the Families...Colubridæ Aglyphæ, part. Trustees of the British Museum (Natural HIstory). (Taylor and Francis, Printers.) London. xiii + 448 pp. + Plates I.- XXVIII. (Tropidonotus cyclopium [sic], pp. 244-245.)
↑ Schmidt, K.P., and D.D. Davis. 1941. Field Book of Snakes of the United States and Canada. G.P. Putnam's Sons. New York. xiii + 365 pp. (Natrix cyclopion, pp. 215-217, Figure 70. + Plate 23, Top, on p. 343.)
↑ Smith, H.M., and E.D. Brodie, Jr. 1982. Reptiles of North America: A Guide to Field Identification. Golden Press. New York. 240 pp. ISBN 0-307-13666-3 (paperback). (Nerodia cyclopion, pp. 154-155.)
