George Boolos and Vann McGee. The degree of the set of sentences of predicate provability logic that are true under every interpretation. The journal of symbolic logic, vol. 52 (1987), pp. 165–171.
Albert Visser · Journal of Symbolic Logic · 1991
George Boolos and Vann McGee. The degree of the set of sentences of predicate provability logic that are true under every interpretation. The journal of symbolic logic, vol. 52 (1987), pp. 165–171. - Volume 56 Issue 1