Title: The Cut Elimination and the Nonlengthening Property for the Sequent Calculus with Equality,
Abstract: We show how Leibnitz.s indiscernibility principle and Gentzen's original work
lead to extensions of the sequent calculus to first order logic with equality
and investigate the cut elimination property. Furthermore we discuss and
improve the nonlengthening property of Lifshitz and Orevkov.