The link is to a reprint of the paper in the Scientific American Supplement, No. 1665, November 30, 1907, p.348-350, copied on Thomas H. White's United States Early Radio History website
De Forest patented a number of variations of his detector tubes starting in 1906. The patent that most clearly covers the Audion is U.S. Patent 879,532, Space Telegraphy, filed January 29, 1907, issued February 18, 1908
De Forest va patentar moltes variacions de tubs des del 1906. La patent amb major claredat de l'audió és la U.S. PAtent 879,532,del 29 de gener del 1907.
