1. Boolos, G. and R. Jeffrey, Computability and logic, Second Edition, Cambridge University Press, New York. Zbl 0298.02003 MR 82d:03001
2. Cutland, N., Computability, Cambridge University Press, New York, 1980. Zbl 0448.03029 MR 81i:03001
3. Dummett, M., Elements of Intuitionism, Clarendon Press, Oxford, 1977. Zbl 0358.02032 MR 58 #16194
4. Friedman, H., “Classically and intuitionistically provably recursive functions,” pp. 21–27 in Higher Set Theory, edited by G. Müller and D.S. Scott, Springer-Verlag, New York, 1978. Zbl 0396.03045 MR 80b:03093
5. Gödel, K., “On the completeness of the calculus of logic,” pp. 61–101 in Collected Works, Volume I, Publications 1929–1936, edited by S. Feferman et al., Oxford University Press, New York, 1986.