This work is in the public domain in the United States because it was legally published within the United States (or the United Nations Headquarters in New York subject to Section 7 of the United States Headquarters Agreement) before 1964, and copyright was not renewed.
- For Class A renewals records (books only) published between 1923 and 1963, check the Stanford University Copyright Renewal Database.
- For other renewal records of publications between 1922–1950 see the University of Pennsylvania copyright records scans.
- For all records since 1978, search the U.S. Copyright Office records.
