References:

1  International Committee on Radiation Protection (ICRP). Annals of the ICRP. Publication 80. Pergamon Press, New York, NY. 1998;28: N 3, page 73.

2  The Mayo Clinic Manual of Nuclear Medicine. Michael K. Oconnor, Editor. Mayo Clinic Foundation. Churchill Livingstone, New York, USA, 1996. Page 215.