Delvinquier, .L.J.; Patterson, D.J. (1993). "The opalines". In Kreier, Julius P.; Baker, John R. (eds.). Parasitic Protozoa. Vol. 3 (2nd ed.). Academic Press. pp. 247–325. ISBN978-0-12-426013-9.
Corliss, J.O. (1955). "The opalinid infusorians: Flagellates or ciliates?". Journal of Protozoology. 2 (3): 107–114. doi:10.1111/j.1550-7408.1955.tb02410.x.
Kostka M, Hampl V, Cepicka I, Flegr J (2004). "Phylogenetic position of Protoopalina intestinalis based on SSU rRNA gene sequence". Mol. Phylogenet. Evol. 33 (1): 220–4. doi:10.1016/j.ympev.2004.05.009. PMID15324850.
Affa'a, F.-M.; Mignot, J.-P.; Amiet, J.-L. (1996). "Morphological and cytological observations on two opalinid endocommensals of Acanthixalus spinosus (Amphibia, Anura)". Canadian Journal of Zoology. 74 (8): 1573–84. doi:10.1139/z96-171.
El Mofty MM, Sadek IA (1975). "The effect of fresh toad bile on the induction of encystation in Opalina sudafricana parasitic in Bufo regularis". Int. J. Parasitol. 5 (2): 219–24. doi:10.1016/0020-7519(75)90032-6. PMID803935.
Sandon, H. (1980). "Notes on African opalinids (Protozoa, Opalinata). 1. Zelleriella spp". Systematic Parasitology. 1 (3–4): 171–188. doi:10.1007/BF00009844.
Kostka M, Hampl V, Cepicka I, Flegr J (2004). "Phylogenetic position of Protoopalina intestinalis based on SSU rRNA gene sequence". Mol. Phylogenet. Evol. 33 (1): 220–4. doi:10.1016/j.ympev.2004.05.009. PMID15324850.
El Mofty MM, Sadek IA (1975). "The effect of fresh toad bile on the induction of encystation in Opalina sudafricana parasitic in Bufo regularis". Int. J. Parasitol. 5 (2): 219–24. doi:10.1016/0020-7519(75)90032-6. PMID803935.