08/20/1877 [Supplied year, month, and day] Edison, Thomas Alva to Preece, William Henry
(Prescott, George Bartlett) Music; Multiple telegraphy (duplex, quadruplex); Telephone
[Z005]  Institution of Electrical Engineers Archives, London, UK: William H. Preece Papers
[Z005AD; TAEM 0:0]
Courtesy of the Institution of Electrical Engineers Archives.