| st[rk] = st0[rk], rk ∈ st, rk ∈ st0 ⊦ r = rk .ref, r ∈ st, rk ∈ st0 -- r |
⊦ r -- sk ∈ st -- r0 ↔ r ≠ r0 ∧ r -- sk ∈ st
⊦ r -- sk ∈ st → r ∈ st
[[CONCRETESIMPRULES : ([CSIMPSEQ : ⊦ ¬ rk ∈ st → st[rk] = ∅[rk]], [CSIMPELIM : ⊦ r = rk .ref ∧ sk = rk .key ↔ rk = r -- sk])], [EXTRATERMS : (rk, r0, sk)]]