1. (1) S. Okada and N. Momoshima, Health Phys. 65, 595 (1993).
2. (2) T. Okai, N. Momoshima, and Y. Takashima, J. Radioanal. Nucl. Chem. 239, 527 (1999).
3. (3) N. Momoshima, M. Takamura, Y. Nagao, T. Toyoshima, T. Okai, and T. Uda, Radioecology and Environmental Dosimetry, Eds. J. Inaba, H. Tsukada, and A. Takeda, Institute for Environmental Sciences, Rokkasho (2004), p 416.
4. (4) T. Okai and Y. Takashima, J. Radioanal. Nucl. Chem. 130, 399 (1989).
5. (5) Technical support document for the 1992 citizen's guide to radon, U. S. Environmental, Protection, and Agency, Washington D. C., EPA 400-R-92-011 (1992).