Relationship between blood groups of  ABO system and the severity of duodenal ulcers.
D000017:ABO Blood-Group System; D001789:Blood Group Antigens; D003604:Czechoslovakia; D004381:Duodenal Ulcer / Q000453:epidemiology*; D006801:Humans
D000017:ABO Blood-Group System; D001789:Blood Group Antigens