XCB, the Last of the Shortest Single Axioms for the Classical Equivalential Calculus
|Title||XCB, the Last of the Shortest Single Axioms for the Classical Equivalential Calculus|
|Year of Publication||2002|
|Authors||Wos, L, Ulrich, D, Fitelson, B|
|Series Title||Bull. Section Logic|
It has long been an open question whether the formula XCB = EpEEEpqErqr is, with the rules of substitution and detachment, a single axiom for the classical equivalential calculus. This paper answers that question affirmatively, thus completing a search for all such eleven-symbol single axioms that began seventy years ago.