Okamoto T. Fossil Periglacial Phenomena on Karst in the late Quaternary in the Akka Karst, Northeastern Japan. Geog. Fis. Dinam. Quat. 1998;3(4):61-67. Accessed April 29, 2026. https://www.gfdq.glaciologia.it/index.php/GFDQ/article/view/1196