Proof with try solve [simpl; auto|congruence].
intros. revert acc R H0 H1. induction l.
intros acc R H0 H1. simpl in H1; inversion H1; subst...
intros acc R H0 H1. simpl in H; destruct H.
simpl in H1. destruct a. if_tac in H1.
inversion H1; subst. apply IHl with (R:=R)(acc:=acc)...
remember (clause_generate R (PureClause gamma delta priority prio_ok)) as b.
destruct b. destruct p. destruct p. apply IHl with (R:=(v,e)::R)(acc:=c::acc)...
simpl. split. eapply clause_generate_sound; eauto. auto.
congruence. inversion H1; subst... inversion H1; subst...
Qed.

(* Specifications: *)
Lemma partial_mod_sound2 R R' acc l c ce s :
listd clause_denote inter TT l s -> listd clause_denote inter TT acc s ->
partial_mod R acc l = inr _ (R', c, ce) -> clause_denote c s.