1. International Commission of Radiological Protection (1991) Recommendation of the International Commission on Radiological Protection, ICRP Publication 60
2. National Council on Radiation Protection and Measurements (1987) Radiation exposure of the U.S. population from consumer products and miscellaneous sources, NCRP report 95
3. European commission (1995) Study on consumer products containing radioactive substances in the EU Member States, RP 68
4. European commission (2007) Study on consumer products containing radioactive substances in the EU Member States, RP 146
5. Yosida M, Endou A, Satou S, Ohhata T, Watanabe M, Ohyama R, Furuya H (2005) Trans Atomic Energy Soc Jpn 4:213