1. L. Wittgenstein, Philosophical Investigations, Blackwell, Oxford, 1953.
2. F. Waismann, The Principles of Linguistic Philosophy, Macmillan, London, 1964, Ch. V.
3. E. Mach, The Analysis of Sensations, new edition, Dover, New York, 1959, and has been extensively criticized, cf.
4. A. C. Lloyd, ‘Empiricism, Sense Date and Scientific Language’, Mind, 59, 57–70
5. P. Alexander, Sensationalism and Scientific Explanation, London, 1963.