original descriptionChamberlin, R. V. (1951). Eleven new western millipeds. <em>Natural History Miscellanea.</em> 87: 1-12. page(s): 8 [details]
additional sourceShear, William Albert. (2011). Cave millipeds of the United States. XI. Opiona graeningi, n. sp., a troglomorphic caseyid milliped from Siskiyou County, California, with comments on the genus Opiona Chamberlin 1951 (Diplopoda, Chordeumatida, Caseyidae). Zootaxa, 3114: 50-56[details]
additional sourceShear, W. A.; Crawford, R. L. (2019). Cave millipedes of the United States. XVI. Two new species from Oregon Caves National Monument, Oregon (Chordeumatida, Conotylidae and Caseyidae). <em>Zootaxa.</em> 4674 (5): 571–580., available online athttps://doi.org/10.11646/zootaxa.4674.5.6[details] Available for editors
additional sourceGardner, M. R.; Shelley, R. M. (1989). New records, species and genera of Caseyid Millipeds from the Pacific Coast of North America (Diplopoda: Chordeumatida: Caseyidae). Pan-Pacific Entomologist, 65(2): 177-268. SanFrancisco[details]