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Snider DE, Comstock GW, Martinez I, Caras GJ.Snider DE, et al. Among authors: comstock gw.J Natl Cancer Inst. 1978 Apr;60(4):785-8. doi: 10.1093/jnci/60.4.785.J Natl Cancer Inst. 1978.PMID: 344899Clinical Trial.