1. Research on guidance devices for the blind,1946
2. Electronic guiding aids for blind people;Beurle;Electronic Engineering,1951
3. Orientation of bats and men by ultrasonic echo location;Kay;British Communications and Electronics,1961
4. Auditory perception and its relation to ultrasonic blind guidance aids;Kay;J. British Institution of Radio Engineers,1962
5. Medical electronics, part IV: Prosthetics-hearing aids and blind guidance devices;Busher;Electronics,1961