1. BÉKÉSY, G. von.Experiments in hearing. New York: McGraw-Hill, 1960.
2. EKMAN, G.Subjective power functions and the method of fractionation. Report from the Psychological Laboratory, University of Stockholm, 1956, No. 34.
3. FLETCHER, H., & MUNSON, W. A. Loudness, its definition, measurement and calculation. Journal of the Acoustical Society of America, 1933,5, 82–108.
4. FRANZÉN, O. On summation: A psychophysical study of the tactual sense. In“Quarterly Progress and Status Report,” Speech Transmission Laboratory, Royal Institute of Technology. Stockholm, Sweden, January 15, 1966.
5. GELDARD, F. A. Cutaneous channels of communication. In W. A. Rosenblith (Ed.),Sensory communication. New York: Wiley, 1961. Pp.73–87.