1. International Commission on Radiological Units (1950) Recommendations, London.
2. International Commission on Radiological Units, (1975) Am. J. Roentgend.
125(2), 492.
3. Oddie, T. H. (1937) Brit. J. Radiol, 10, 348.
4. Dawson, J. A. T. (1946) J. Sci. Instrum., 23, 138.
5. Russ, S. and Jennings, W. A. (1948) Radon: Its Technique and Use, Murray, London.