title: Letter: Concentrates of clotting-factor IX.
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D004341:Drug Evaluation; D005164:Factor IX / Q000627:therapeutic use*; D005169:Factor VIII / Q000037:antagonists & inhibitors; D006467:Hemophilia A / Q000188:drug therapy*; D006801:Humans; D011516:Prothrombin / Q000627:therapeutic use*
chemical_list: D011516:Prothrombin; D005169:Factor VIII; D005164:Factor IX