190 RADIATION BIOLOGY 



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gamma rays. Radiology, 56: 229-241. 

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 WPA, Federal Works Agency, New York City (1940) Tables of sine, cosine, and 



exponential integrals. 

 Wrenshall, G. A., and H. J. Nichols (1942) Secondary radiation from X-ray filters. 



L Single metal filters. Can. J. Research, A20: 185-194. 



Manuscript received by the editor Feb. 4, 1952 



