| ∃∃J,L,V. ⦃G1,L,V⦄ ⬂*[b] ⦃G2,L2,T2⦄ & L1 = L.ⓑ{J}V & i = 0
| ∃∃J,L,j. ⦃G1,L,#j⦄ ⬂*[b] ⦃G2,L2,T2⦄ & L1 = L.ⓘ{J} & i = ↑j.
#b #G1 #G2 #L1 #L2 #T2 #i #H elim (fqus_inv_fqu_sn … H) -H * /3 width=1 by and3_intro, or3_intro0/
| ∃∃J,L,V. ⦃G1,L,V⦄ ⬂*[b] ⦃G2,L2,T2⦄ & L1 = L.ⓑ{J}V & i = 0
| ∃∃J,L,j. ⦃G1,L,#j⦄ ⬂*[b] ⦃G2,L2,T2⦄ & L1 = L.ⓘ{J} & i = ↑j.
#b #G1 #G2 #L1 #L2 #T2 #i #H elim (fqus_inv_fqu_sn … H) -H * /3 width=1 by and3_intro, or3_intro0/