1. 3) Isshiki, N. (1982) Geology of the Kozushima district. Quadrangle series scale 1:50,000. Geol. Surv. Japan, Hachijojima (9) No. 2 (in Japanese).
2. 5) Tsuya, H. (1930) Geographical features and the geological structure of Izu Kozushima volcanic island, Japan. Geogr. Rev. Jpn. 3, 453–469 (in Japanese).