Birch, R A technique for measuring the variation of photon spectrum from X-ray generators over the mains voltage cycle. [electronic resource] - Physics in medicine and biology Sep 1976 - 745-53 p. digital Publication Type: Journal Article ISSN: 0031-9155 Standard No.: 10.1088/0031-9155/21/5/003 doi Subjects--Topical Terms: Elementary ParticlesSpectrum AnalysisTechnology, RadiologicX-Rays