1. Aono, H. (1985) Geologic structure of the Ashio and Yamizo Mountains with special reference to its tectonic evolution. Sci. Rep. Inst. Geosci., Univ. Tsukuba, 6, 21–57.
2. Conodonts at the Permian-Triassic boundary in Japan:Conodonts from the basal part of the Adoyama formation
3. De Wever, P., Dumitrica, P., Caulet, J. P., Nigrini, C. and Caridroit, M. (2001) Radiolarians in the Sedimentary Record. Gordon and Breach Science Publishers, Singapore, 533p.
4. Fujimoto, H. (1961) Explanatory text of the Geological map of Japan, Scale 1:50,000, Tochigi. Geol. Surv. Japan. 62p. (in Japanese with English Summary 6p.)
5. Geological Survey of Japan, AIST (2018) Seamless digital geological map of Japan 1: 200,000. January 10, 2018 version. Geol. Surv. Japan, AIST. https://gbank.gsj.jp/seamless/v2full/ (accessed 2018-2-1)