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2. Mixed radionuclide gamma-ray reference standard Code QCY.44;Amersham,1985
3. Instruments catalog;Canberra,1992
4. Determination of U and Ra in rock samples by gamma-spectrometric method;Chouak;J. Radioanal. Chem.,1978
5. Gamma and x-ray spectrometry with semiconductor detectors;Debertin,1988