The New York Public Library believes that this item is in the public domain under the laws of the United States. A search of the U.S. Catalogs of Copyright Entries indicates that the copyright of Dance Observer was registered, but not renewed.
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 (70 years p.m.a.), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties.