| validref(str, refs .first, ty, st), validrefs(str0, refs, st[refs .first -- _type] .type, st), level⊆(str, str0) ⊦ refs = [], refs .first = refs .last, path∃(str, refs .first, refs .last, st), dups(refs) |
refs = r + refs0, validref(str, r, ty, st), validrefs(str0, refs, st[r -- _type] .type, st), level⊆(str, str0) ⊦ refs = [], r = refs .last, path∃(str, r, refs .last, st), dups(refs)
[[CONCRETESIMPRULES : ([CSIMPELIM : refs ≠ [] ⊦ r = refs .first ∧ refs0 = refs .rest ↔ refs = r + refs0])], [EXTRATERMS : (refs, r, refs0)]]