This file is in the public domain because This file is in the public domain, because This work is in the public domain in the United States because it was published in the United States between 1923 and 1977 without a copyright notice. See Commons:Hirtle chart for further explanation. Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (50 p.m.a.), Mainland China (50 p.m.a., not Hong Kong or Macao), Germany (70 p.m.a.), Mexico (100 p.m.a.), Switzerland (70 p.m.a.), and other countries with individual treaties.