1. Sheaf representation for topoi;Awodey;J. Pure Appl. Algebra,2000
2. Philosophical reflections on the foundations of mathematics;Couture;Erkenntnis,1991
3. The Philosophy of Mathematics;Hintikka,1969
4. Introduction to Metamathematics;Kleene,1952
5. S. Kripke, Is there a problem about substitutional quantification? in: Evans, MacDowell (Eds.), Truth and Meaning, Clarendon Press, Oxford, 1976, pp. 325–419.