3 problems

Let derivations be derivations in natural deduction, and let a derivation be reduced to a normal form by the normalization procedures of the system. Prawitz's Normalization Conject…

Let derivations be derivations in a natural-deduction system, and let two derivations be equivalent when they have the same assumptions and conclusion and belong to the reflexive,…

Let $\Pi$ be a derivation in the natural-deduction system $\mathsf{NK}$, and consider the reduction steps described in the paper's rewriting system. A derivation is called “standar…