1. Bressan, A. (1972). A general interpreted modal calculus. Yale University Press.
2. Crossley, J. N. & Humberstone, I. L. (1977). The logic of “actually”. Reports on Mathematical Logic, 8, 11–29.
3. Fitting, M. (1972). An epsilon-calculus system for first-order S4. In W. Hodges (Ed.), Conference in mathematical logic, london ‘70 (pp. 103–110). Springer Lecture Notes in Mathematics (Vol. 255). Springer.
4. Fitting, M. (1973). A modal logic analog of Smullyan’s fundamental theorem. Zeitschrift für mathematische Logik und Gründlagen der Mathematik, 19, 1–16.
5. Fitting, M. (1975). A modal logic epsilon-calculus. Notre Dame Journal of Formal Logic, 16, 1–16.