02/16/1877 [Supplied year] Dolbear, Amos Emerson to Bell, Alexander Graham
(Watson, Thomas Augustus) Testing and quality control; Telegraph; Telephone
[X012H]  AT&T Archives and History Center, Warren, N.J.: General Manager's Letterbooks (Boxes 57-59)
[X012HA; TAEM 0:0]
Courtesy of the AT&T Archives and History Center.