MAYBE ignored inputs: (COMMENT rules to obtain PNF of first-order formulas with conjunctions and universal quantifiers + commutativity rule of universal quantifiers ) (COMMENT Example 12 of [ Suzuki et al. , SCSS 2016 ] ) NRS: [ (0): a#Y1 |- (and <(forall [a][]X1),[]Y1>) -> (forall [a](and <[]X1,[]Y1>)), (1): a#X2 |- (and <[]X2,(forall [a][]Y2)>) -> (forall [a](and <[]X2,[]Y2>)), (2): |- (forall [a](forall [b][]X)) -> (forall [b](forall [a][]X)) ] Check confluence by Knuth-Bendix criterion uniform writing to temporary file... ./run_snprover.sh ./SMLNJ-v053we.trs NO Problem: and(pair_2(forall(lambda(X1)),Y1)) -> forall(lambda(and(pair_2(X1,Y1)))) and(pair_2(X2,forall(lambda(Y2)))) -> forall(lambda(and(pair_2(X2,Y2)))) forall(lambda(forall(lambda(X)))) -> forall(lambda(forall(lambda(X)))) Proof: Containment Processor: loop length: 1 terms: forall(lambda(forall(lambda(X)))) context: [] substitution: X -> X Qed termination proof failed result: MAYBE time: 0 msec.