1. J. Barwise, J. Etchemendy, Language Proof and Logic (Seven Bridges Press, New York, 2000)
2. J.L. Bell, Hilbert’s $$\varepsilon$$ -operator and classical logic. J. Philos. Log. 22, 1–18 (1993)
3. J.L. Bell, Hilbert’s $$\varepsilon$$ -operator in intuitionistic type theories. Math. Log. Q. 39, 323–337 (1993)
4. G. Berkeley, A Treatise Concerning the Principles of Human Knowledge (Open Court, Chicago, 1904) [Originally published 1710]
5. A. Church, Introduction to Mathematical Logic (Princeton University Press, Princeton, 1956)