1. Bernard Becker Medical Library Washington University School of Medicine. Deafness in disguise-2002 timeline of hearing devices and early deaf education . Accessible at: http://beckerexhibits.wustl.edu/.
2. Development of a hearing aid system with independently adjustable subranges of its spectrum using microprocessor hardware;Graupe D.;Bulletin of Prosthetics Research,1975
3. A self-adaptive noise filtering system;Graupe D.;Hearing Instruments,1986
4. A Historical Perspective on Digital Hearing Aids: How Digital Technology Has Changed Modern Hearing Aids