1. W. S. Jevons, The Principles of Science, London, 1924.
2. K. Popper, The Open Society and Its Enemies, Ch. 25, London, 1945.
3. C. J. Ducasse, “Explanation, Mechanism and Teleology”, The Journal of Philosophy, XXII (1925), 150–155.
4. H. Feigl, “Operationism and Scientific Method”, Psychological Review, vol. 52 (1945), pp. 250–9.
5. H. Hospers, “On Explanation”, The Journal of Philosophy, vol. 43 (1946), pp. 337–356.