1. Admissible Sets and Structures;Barwise,1975
2. Foundations of Constructive Analysis;Bishop,1967
3. “Eine Interpretation des Intuitionistischen Aussagenkalkuls”;Gödel;Ergebnisse eines mathematischen Kolloquiums,1932
4. “Disjunction and Existence under Implication in Elementary Intuitionistic Systems”;Kleene;Journal of Symbolic Logic,1962
5. “Some Remarks on the Notion of Proof”;Myhill;Journal of Philosophy,1960