1. Artemov, 1986, On Modal Logics axiomatizing Provability, Math. USSR Izvestia, Vol 27, No.3, 401?429.
2. Bennet, J.H., 1962, On spectra, Thesis, Princeton University, Princeton.
3. Buss, S., 1985, Bounded Arithmetic, Thesis, Princeton University, Princeton. Reprinted: 1986, Bibliopolis, Neapoli.
4. Berarducci, A., The interpretability Logic of Peano Arithmetic, Manuscript, 1988.
5. Feferman, S., 1960, em Arithmetization of metamathematics in a general setting, Fund. Math. 49, 33?92.