Topic propositional Logical System gentzen Or Elimination and Bi-Conditional Introduction 12/23/05 Or Elimination Your browser does not support html5 video. Bi-Conditional Introduction Your browser does not support html5 video. Book traversal links for Help with Or Elimination and Bi-conditional Introduction ‹ Tutorial 9: The Remaining Sentential Rules of Inference Up Example of a Harder Sentential Proof ›