T. Hawksley. Catalogue of otacoustical instruments to aid the deaf.. 3rd ed. London : T. Hawksley, .
GENERAL MEDICAL CATALOGUES
George Tiemann & Co.; American Armamentarium Chirurgicum. Catalogue of surgical instruments #31 orginally published in 1889. Facsimile reprinted text available from Norman Publishing, San Francisco, 1989.
Sensory Aids, 1880-present; Approximately 120 items;Consists primarily of hearing aids ranging from ear trumpets, to large microphones that hung around the user's neck, to the modern designs that clip onto the ear.