. "http://clinicaltrials.gov/ct2/show/NCT00000500?rank=11". . "ClinicalTrials.gov"@en. _:npLyLFFw1571 "physicians_health_study". _:npLyLFFw1571 . "NCT00000500"@en. . _:npLyLFFw1571. . . . . . "40"^^. . . . . "84"^^. . . . . "Source: Freebase - The World's database". "Physicians' Health Study"@en. . "No current usage of aspirin or Vitamin A tables greater than once per week."@en. "No history of stroke, myocardial infarction, cancer, or renal disease."@en. "No contraindications to aspirin or beta-carotene"@en. . "Male physicians"@en. . . "1981-09". .