↑ Hartley, H. A. (1958). “High fidelity”. Audio Design Handbook (PDF). New York, New York: Gernsback Library. tr. 200. Library of Congress Catalog Card No. 57-9007. Truy cập ngày 8 tháng 8 năm 2009. I invented the phrase 'high fidelity' in 1927 to denote a type of sound reproduction that might be taken rather seriously by a music lover. In those days the average radio or phonograph equipment sounded pretty horrible but, as I was really interested in music, it occurred to me that something might be done about it.
↑ Gustav Büscher, A. Wiegemann: Kleines ABC der Elektroakustik. 6. Aufl. Franzis, München 1972. ISBN 3-7723-0296-3
