References
- Gravendeel D. W. Perceptive Bass-deafness. H. J. Smits, Utrecht 1958
- Fletscher H. Hearing, Stevens, Davis. John Wiley, New York 1948; 185
- Katsuki. Keidel, Internat. Audiology 1962; Bd. 1: 43–45
- Langenbeck B. Lehrbuch der praktischen Audiometrie. Georg Thieme, Stuttgart 1963; 157 ff