Design and methodological considerations in the National Cooperative Gallstone Study: a multicenter clinical trial.
D000328:Adult; D000368:Aged; D001706:Biopsy; D002769:Cholelithiasis / Q000188:drug therapy*; D002986:Clinical Trials as Topic / Q000379:methods*; D003201:Computers; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008099:Liver / Q000473:pathology; D008111:Liver Function Tests; D008875:Middle Aged; D011786:Quality Control; D011897:Random Allocation