End SUBST_SOUND.
Module Subst_Sound (VSD: VERISTAR_DEFS) : SUBST_SOUND with Module VSD := VSD.
Module VSD := VSD.

(*Substitution Lemmas*)
Lemma subst_expr_sound : forall i e e' s,
(subst_expr i e e' ==
match e' with Nil => Nil | Var x  => if Var.eq_dec i x then e else e'
end) s.