1. AYER, A. J., Language Truth and Logic (2nd edition). London 1946, 160
2. On Padoa's method in the theory of definition;Beth;Indagationes Mathematicae,1953
3. Scientific Explanation.;Braithwaite,1953
4. Physics The Elements.;Campbell,1920
5. CARNAP, R., Logical Foundations of Probability. Chicago 1950, XVIII + 607 PP