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This work is in the public domain because it was published in the United States between 1929 and 1963, and although there may or may not have been a copyright notice, the copyright was not renewed. For further explanation, see Commons:Hirtle chart and the copyright renewal logs. 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. العربية ∙ Deutsch ∙ English ∙ español ∙ français ∙ galego ∙ italiano ∙ 日本語 ∙ 한국어 ∙ македонски ∙ português ∙ português do Brasil ∙ русский ∙ sicilianu ∙ slovenščina ∙ українська ∙ 简体中文 ∙ 繁體中文 ∙ +/−

The copyright has definitely expired in the USA and is now in the public domain. US. copyright May 23 1937 by Edwin Fitch Northrup, who died in 1940. Copyright was not renewed in 1965 (28 years statutory time window). Verified by researching Zero..., Northrup..., and Pseudoman... in the Copyright Card Catalog, Library of Congress, Madison Building Room LM-410. Pictures of the actual file cards surrounding the nonexistent renewal cards are available on request. The public domain book was scanned by Black Cat Press and reprinted on Lulu. The picture has no separate copyright notice, and is likely Dr. Northrup's own photography.