1. Set existence;Gandy, R. O.;Bull. Acad. Polon. Sci. S\'{e}r. Sci. Math. Astronom. Phys.,1960
2. The classical and the 𝜔-complete arithmetic;Grzegorczyk, A.;J. Symbolic Logic,1958
3. Hierarchies of number-theoretic predicates;Kleene, S. C.;Bull. Amer. Math. Soc.,1955
4. Quantification of number-theoretic functions;Kleene, S. C.;Compositio Math.,1959
5. Arithmetical predicates and function quantifiers;Kleene, S. C.;Trans. Amer. Math. Soc.,1955