O. M.  Amin and Heckmann, R. A., ?Description and host relationships of Polymorphus spindlatus n. sp. (acanthocephala: polymorphidae) from the heron Nycticorax nycticorax in Peru?, Journal of ParasitologyJ. PARASITOL., vol. 77, no. 2, pp. 201 - 205, 1991.

O. M.  Amin and Heckmann, R. A., ?Description and host relationships of Polymorphus spindlatus n. sp. (Acanthocephala: Polymorphidae) from the heron Nycticorax nycticorax in Peru.?, J Parasitol, vol. 77, no. 2, pp. 201-5, 1991.