--- /dev/null
+(**************************************************************************)
+(* ___ *)
+(* ||M|| *)
+(* ||A|| A project by Andrea Asperti *)
+(* ||T|| *)
+(* ||I|| Developers: *)
+(* ||T|| The HELM team. *)
+(* ||A|| http://helm.cs.unibo.it *)
+(* \ / *)
+(* \ / This file is distributed under the terms of the *)
+(* v GNU General Public License Version 2 *)
+(* *)
+(**************************************************************************)
+
+include "basic_2/relocation/frees.ma".
+
+(* CONTEXT-SENSITIVE FREE VARIABLES *****************************************)
+
+(* Main inversion lemmas ****************************************************)
+
+theorem frees_mono: ∀L,T,f1. L ⊢ 𝐅*⦃T⦄ ≡ f1 → ∀f2. L ⊢ 𝐅*⦃T⦄ ≡ f2 → f1 ≗ f2.
+#L #T #f1 #H elim H -L -T -f1
+[ /3 width=2 by frees_inv_atom, isid_inv_eq_repl/
+| /4 width=5 by frees_inv_sort, eq_push_inv_isid, isid_inv_eq_repl, eq_trans/
+| #I #L #V #f1 #_ #IH #x #H elim (frees_inv_zero … H) -H *
+ [ #H destruct
+ | #Z #Y #X #f2 #Hf2 #H1 #H2 destruct /3 width=5 by eq_next/
+ ]
+| #I #L #V #i #f1 #_ #IH #x #H elim (frees_inv_lref … H) -H *
+ [ #H destruct
+ | #Z #Y #X #f2 #Hf2 #H1 #H2 destruct /3 width=5 by eq_push/
+ ]
+| /4 width=5 by frees_inv_gref, eq_push_inv_isid, isid_inv_eq_repl, eq_trans/
+| #I #L #V #T #p #f1 #f2 #f #_ #_ #Hf #IHV #IHT #g #H elim (frees_inv_bind … H) -H
+ #g1 #g2 #HV #HT #Hg @(sor_mono … Hf) -Hf
+ /5 width=3 by sor_eq_repl_fwd2, sor_eq_repl_fwd1, tl_eq_repl/ (**) (* full auto too slow *)
+| #I #L #V #T #f1 #f2 #f #_ #_ #Hf #IHV #IHT #g #H elim (frees_inv_flat … H) -H
+ #g1 #g2 #HV #HT #Hg @(sor_mono … Hf) -Hf
+ /4 width=3 by sor_eq_repl_fwd2, sor_eq_repl_fwd1/ (**) (* full auto too slow *)
+]
+qed-.