| hasSharing(r ' + refs, st) ⊦ hasSharing(refs, st), hasSharing(r, st) |
⊦ hasSharing(refs, st) ↔ (∃ r. r ∈ refs ∧ hasSharing(r, st))
∃ r0. r0 ∈ r ' + refs ∧ hasSharing(r0, st) ⊦ hasSharing(refs, st), hasSharing(r, st)
[[CONCRETESIMPRULES : ()], [EXTRATERMS : (st, r ' + refs)]]