Commutativity Theorems in CL-Semirings R. Padmanabhan and Yang Zhang Abstract (corrected version): There are many conditions known which force a ring to be commutative. Such theorems are known as "commutativity theorems". Here we generalize some of the commutativity theorems to cancellative semirings, i.e. semirings in which the addition is cancellative. We use Prover9 to give first order proofs without actually going through the quotient construction.