The calendar and duodenal ulcer.
D004381:Duodenal Ulcer / Q000150:complications / Q000453:epidemiology*; D006801:Humans; D006973:Hypertension / Q000150:complications; D010438:Peptic Ulcer Hemorrhage / Q000453:epidemiology; D010439:Peptic Ulcer Perforation / Q000453:epidemiology; D010507:Periodicity; D012621:Seasons; D013997:Time Factors; D014481:United States