Disinfection of mail in the United States.
D004203:Disinfection / Q000266:history*; D049670:History, 17th Century; D049671:History, 18th Century; D049672:History, 19th Century; D049673:History, 20th Century; D011177:Postal Service / Q000266:history*; D013242:Sterilization / Q000266:history*; D014481:United States