KIGOSHI, K. (1967) Ionium dating of igneous rocks. Science, 156, 932-934.
MACHIDA, H. and ARAI, F. (1979) Daisen Kurayoshi Pumice: stratigraphy, chronology, distribution and implication to Late Pleistocene events in Central Japan. Jour. Geography, 88, 315-330. (in Japanese with English abstract)