1. ICRU Report 21, 1972. Radiation Dosimetry: Electrons with Initial Energies between 1 and 50 MeV, pp.47 (ICRU Publications, Washington D.C.).
2. PRICE, B. T., HORTON, C. C , and SPINNEY, K. T., 1957. Radiation Shielding, pp.74-76 (Pergamon Press, London).
3. Back-scattering from metals in superficial therapy with high energy electrons