Ruppert, E.E.; Fox, R.S & Barnes, R.D. (2004). Invertebrate Zoology (7th ed.). Brooks/Cole. pp. 213–215. ISBN 0-03-025982-7. 0-03-025982-7
Ruppert, E.E.; Fox, R.S & Barnes, R.D. (2004). Invertebrate Zoology (7th ed.). Brooks/Cole. pp. 213–215. ISBN 0-03-025982-7. 0-03-025982-7
Pechenik, Jan A. (2009). Biology of the Invertebrates. McGraw-Hill Higher Education. pp. 150–151. ISBN 9780073028262. 9780073028262