The evolution of trial registration.
D002986:Clinical Trials as Topic / Q000592:standards* / Q000639:trends; D006801:Humans; D009317:National Library of Medicine (U.S.) / Q000592:standards / Q000639:trends; D012042:Registries / Q000592:standards*; D014481:United States; D014486:United States Food and Drug Administration / Q000592:standards / Q000639:trends