Kawakatsu, M.; Oki, I.; Tamura, S.; Sugino, H. (1976). Studies on the morphology, karyology, and taxonomy of the Japanese freshwater planarian Dugesia japonica Ichikawa et Kawakatsu, with a description of a new subspecies, Dugesia japonica ryukyuensis subspec. nov. Bull Fuji Wom Coll, 14, II: 81-126