1. Proof-theoretic investigations of subsystems of second-order arithmetic;Avigad,1995
2. Foundations of Constructive Mathematics;Beeson,1985
3. The Baire category theorem in weak subsystems of second-order arithmetic;Brown;J. Symbolic Logic,1993
4. Metamathematics of First-Order Arithmetic;Hájek,1991
5. Interpretability and fragments of arithmetic;Hájek,1993