lapply (da_inv_sort … H) -H /3 width=1 by da_sort, deg_next/
| #G #L #K #V #U #W #i #HLK #_ #HWU #IHVW #l #H
elim (da_inv_lref … H) -H * #K0 #V0 [| #l0] #HLK0 #HV0
lapply (da_inv_sort … H) -H /3 width=1 by da_sort, deg_next/
| #G #L #K #V #U #W #i #HLK #_ #HWU #IHVW #l #H
elim (da_inv_lref … H) -H * #K0 #V0 [| #l0] #HLK0 #HV0