1. A. Grzegorczyk, ?Some classes of recursive functions,? Rozpr. Mat.,IV (1953).
2. R. L. Goodstein, Recursive Number Theory, Amsterdam (1957).
3. N. A. Shanin, Recursive Mathematical Analysis; R. L. Goodstein, Calculus of Arithmetic Equalities, Russ. trans. of [2].
4. J. P. Cleave and H. E. Rose, ?n-Arithmetic. Sets, Models and Recursion Theory, Amsterdam (1967).