1. R. Carnap:Philosophical Foundations of Physics (New York, 1966).
2. E. Nagel:The Structure of Science, Chap. V (New York, 1961).
3. H. Putnam:What theories are not, inLogic, Methodology and Philosophy of Science, edited byE. Nagel, P. Suppes andA. Tarski (Stanford, Cal., 1962), p. 140.
4. E. H. Hutten:The Language of Modern Physics (London, 1956), p. 53.
5. D. Bohm: inFoundations of Quantum Mechanics, Rendiconti S.I.F., Course IL, edited byB. d’Espagnat (New York, 1971), p. 443.