fact: Definition equi_unifiable (E1 E2: eqs X) := forall sigma, Unifies sigma E1 <-> Unifies sigma E2.
imports: List Lia Arith Init.Wf Morphisms Program.Program Undecidability.HOU(concon.conservativity calculus.calculus) Undecidability.HOU.unification(systemunification nth_order_unification)