Roth, B., and J. Tupen. “Revision of the Systematic Status of Helminthoglypta walkeriana morroensis (Hemphill, 1911) (Gastropoda: Pulmonata)”. Zootaxa, vol. 616, no. 1, Aug. 2004, pp. 1–23, doi:10.11646/zootaxa.616.1.1.