+(* Basic forward lemmas *****************************************************)
+
+lemma cofrees_fwd_lift: ∀L,U,d,i. L ⊢ i ~ϵ 𝐅*[d]⦃U⦄ → ∃T. ⇧[i, 1] T ≡ U.
+/2 width=1 by/ qed-.
+
+lemma cofrees_fwd_bind_sn: ∀a,I,L,W,U,i,d. L ⊢ i ~ϵ 𝐅*[d]⦃ⓑ{a,I}W.U⦄ →
+ L ⊢ i ~ϵ 𝐅*[d]⦃W⦄.
+#a #I #L #W1 #U #i #d #H #W2 #HW12 elim (H (ⓑ{a,I}W2.U)) /2 width=1 by cpys_bind/ -W1
+#X #H elim (lift_inv_bind2 … H) -H /2 width=2 by ex_intro/
+qed-.
+
+lemma cofrees_fwd_bind_dx: ∀a,I,L,W,U,i,d. L ⊢ i ~ϵ 𝐅*[d]⦃ⓑ{a,I}W.U⦄ →
+ L.ⓑ{I}W ⊢ i+1 ~ϵ 𝐅*[⫯d]⦃U⦄.
+#a #I #L #W #U1 #i #d #H #U2 #HU12 elim (H (ⓑ{a,I}W.U2)) /2 width=1 by cpys_bind/ -U1
+#X #H elim (lift_inv_bind2 … H) -H /2 width=2 by ex_intro/
+qed-.
+
+lemma cofrees_fwd_flat_sn: ∀I,L,W,U,i,d. L ⊢ i ~ϵ 𝐅*[d]⦃ⓕ{I}W.U⦄ →
+ L ⊢ i ~ϵ 𝐅*[d]⦃W⦄.
+#I #L #W1 #U #i #d #H #W2 #HW12 elim (H (ⓕ{I}W2.U)) /2 width=1 by cpys_flat/ -W1
+#X #H elim (lift_inv_flat2 … H) -H /2 width=2 by ex_intro/
+qed-.
+
+lemma cofrees_fwd_flat_dx: ∀I,L,W,U,i,d. L ⊢ i ~ϵ 𝐅*[d]⦃ⓕ{I}W.U⦄ →
+ L ⊢ i ~ϵ 𝐅*[d]⦃U⦄.
+#I #L #W #U1 #i #d #H #U2 #HU12 elim (H (ⓕ{I}W.U2)) /2 width=1 by cpys_flat/ -U1
+#X #H elim (lift_inv_flat2 … H) -H /2 width=2 by ex_intro/
+qed-.
+