1. Röntgen, Sitzber, Würzburger Physik. Medic. Ges. (1895). Translated— Nature, 53, 274 (1896).
2. Richtmyer & Kennard, A Introduction to Modern Physics, 3rd Ed., 469 (1942)
3. Hinsley, A Non-destructive Testing, VIII, Macdonald & Evans (1959).
4. McGonagle, Non-destructive Testing, VI, VII, McGraw Hill (1961).
5. Handbook of Industrial Radiology, Edward Arnold (1949).