+lemma feqg_fquq_trans (S) (b):
+ reflexive … S → symmetric … S → Transitive … S →
+ ∀G1,G,L1,L,T1,T. ❨G1,L1,T1❩ ≛[S] ❨G,L,T❩ →
+ ∀G2,L2,T2. ❨G,L,T❩ ⬂⸮[b] ❨G2,L2,T2❩ →
+ ∃∃G,L0,T0. ❨G1,L1,T1❩ ⬂⸮[b] ❨G,L0,T0❩ & ❨G,L0,T0❩ ≛[S] ❨G2,L2,T2❩.
+#S #b #H1S #H2S #H3S #G1 #G #L1 #L #T1 #T #H1 #G2 #L2 #T2 #H2
+elim(feqg_inv_gen_dx … H1) -H1 // #HG #HL1 #HT1 destruct
+elim (reqg_fquq_trans … H2 … HL1) -L // #L #T0 #H2 #HT02 #HL2
+elim (teqg_fquq_trans … H2 … HT1) -T // #L0 #T #H2 #HT0 #HL0
+lapply (teqg_reqg_conf_sn … HT02 … HL0) -HL0 // #HL0
+/4 width=7 by feqg_intro_dx, reqg_trans, teqg_trans, ex2_3_intro/
+qed-.
+