Global Instance PermutationA_app :
Proper (PermutationA ==> PermutationA ==> PermutationA) (@app A).

Lemma NoDupA_equivlistA_PermutationA l₁ l₂ :
NoDupA eqA l₁ -> NoDupA eqA l₂ ->
equivlistA eqA l₁ l₂ -> PermutationA l₁ l₂.