References
- Aids Hearing. An Experimental Study of Design Objectives, H. Davis, S. S. Stevens, Ft. H. Nichols, C. V. Hudgins, G. E. Peterson, T. J. Marquis, D. A. Ross. Harvard University Press. 1947, by
- Littler T. S. Jn. Sci. Instrum. 1936; 1947
- Littler T. S. Jn. Inst. Elect. Engrs. 1943; 31-3: 67
- Medical Research Council. Hearing Aids and Audiometers. Special Report Series No. 261. HMSO. 1947, London