1. Bureau of Radiological Health, Public Health Service. Population exposure to X-Rays, US 1964. Washington, D.C., Govt Print Off, p 148.
2. Population dose from X-Rays US 1964;Bureau of Radiological Health Public Health Service,1969
3. Principles of radiation protection,1967
4. Russell, W.L.; Russell, L.B.; and Kelley, E.M. Symposium on the intermediate and low level effects of ionizing radiation. London, Taylor and Francis, 1960.
5. Council on Dental Materials and Devices, Council on Dental Research. Radiation hygiene and practice in dentistry III;JADA,1968