Visible speech [by] Ralph K. Potter, George A. Kopp [and] Harriet C. Green. Potter, Ralph Kimball, 1894- Kopp, George Adams, 1900- joint author. Green, Harriet C., 1917- joint author. Deaf Means of communication. Speech. Telephone Equipment and supplies. TK6500 .P65 414 POV Bibliography: p. 430. New York, D. Van Nostrand Co., 1947. 1947. 1947 Text xvi, 441 p. : eng The Bell Telephone Laboratories series Bell Telephone Laboratories series.