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2. Licklider, J. C. R., J. Acoust. Soc. Amer., 27, 996 (1955); Chap. 25 of S. S. Stevens's “Handbook of Experimental Psychology”, see p. 1019 (Wiley, New York).
3. Boer, E. de, “On the ‘Residue’ in Hearing”, thesis, Amsterdam (1956).