1. Extension site of distribution map of radiation dose, etc. (2011) http://ramap.jaea.go.jp/map . Accessed 1 Mar 2012
2. Disaster prevention and nuclear safety network for nuclear environment (2011) Nuclear regulation authority (NRA) http://www.bousai.ne.jp/vis/torikumi/index0301.html
3. Monitoring information of environmental radioactivity level (2011) MEXT http://www.nsc.go.jp/mext_speedi/index_2-1.html . Accessed 1 Mar 2012
4. Abe S (1989) Radiol Sci 34(4):109–113
5. Nakamura T, Banju M, Sato J, Takahashi H (1986) Volcanol Soc Jpn 31(4):253–264