"Hokkaido". Seamless digital geological map of Japan 1: 200,000. The Geological Survey of Japan, AIST. Feb 18, 2010. Archived from the original on 6 January 2013. Retrieved 25 April 2010.
"E-SAN". Quaternary Volcanoes in Japan. Geological Survey of Japan, AIST. 2006. Archived from the original on December 19, 2012. Retrieved 25 April 2010.
archive.today
"E-SAN". Quaternary Volcanoes in Japan. Geological Survey of Japan, AIST. 2006. Archived from the original on December 19, 2012. Retrieved 25 April 2010.
"Hokkaido". Seamless digital geological map of Japan 1: 200,000. The Geological Survey of Japan, AIST. Feb 18, 2010. Archived from the original on 6 January 2013. Retrieved 25 April 2010.