lapply (ltpssa_ltpss_sn … HL1) -HL1 #HL1
lapply (ltpss_sn_dx_trans_eq … HL1 … HL2) -HL1 #HL12
elim (IHL1 … H1) -IHL1 -H1 #U #HU1 #HTU
lapply (ltpssa_ltpss_sn … HL1) -HL1 #HL1
lapply (ltpss_sn_dx_trans_eq … HL1 … HL2) -HL1 #HL12
elim (IHL1 … H1) -IHL1 -H1 #U #HU1 #HTU