1. Intuitionistic modal logic with quantifiers;Fitch;Portuguliae Math.,1948
2. Untersuchungen caber das logische Schliessen;Gentzen;Math. Z.,1935
3. Untersuchungen caber das logische Schliessen;Gentzen;Math. Z.,1935
4. A sheaf approach to models of set theory;Grayson;M.Sc. Thesis,1975
5. Heyting valued models for intuitionistic set theory;Grayson,1979