⊦ adr ∈ ri ↔ (∃ key. key ∈ ri ∧ ri[key] = adr)
∃ key. key ∈ ri ⊖ ks ∧ (ri ⊖ ks)[key] = adr ⊦ adr ∈ ri
Used terms: ri ⊖ ks, adr