04/17/1880 Jehl, Francis -- Technical Notes and Drawings
(Edison, Thomas Alva; Meadowcroft, William Henry) Vacuum and glass bulb
[W100DED]  National Archives, Washington, D.C.: Records of the Patent and Trademark Office (Record Group 241) -- Patent Interference Files -- Boehm v. Edison -- Testimony on Behalf of Edison
[W100DED059D; TAEM 0:0]
Courtesy of the National Archives.