- @(subset_eq_trans β¦ (lift_fsubst β¦))
- [ <structure_append <structure_A_sn <structure_append <structure_L_sn
+ @(subset_eq_trans β¦ (unwind2_term_fsubst_ppc β¦))
+ [ @fsubst_eq_repl [ // | // ]
+ @(subset_eq_trans β¦ (unwind2_term_irefβ¦))
+ @(subset_eq_canc_sn β¦ (lift_term_eq_repl_dx β¦))
+ [ @unwind2_term_grafted_S /2 width=2 by ex_intro/ | skip ] -Ht1
+ @(subset_eq_trans β¦ (lift_unwind2_term_after β¦))
+ @unwind2_term_eq_repl_sn
+(* Note: crux of the proof begins *)
+ <list_append_rcons_sn
+ @(stream_eq_trans β¦ (tr_compose_uni_dx_pap β¦)) <tr_pap_succ_nap
+ @tr_compose_eq_repl
+ [ <nap_unwind2_rmap_append_closed_Lq_dx_depth //
+ | /2 width=2 by tls_succ_unwind2_rmap_append_closed_Lq_dx/
+ ]
+(* Note: crux of the proof ends *)