⊦ H0 = H1 ↔ (∀ r. (r ∈ H0 ↔ r ∈ H1) ∧ (r ∈ H0 → H0[r] = H1[r]))
∀ r. ¬ r ∈ H ⊦ ∀ r. (r ∈ H ↔ r ∈ ∅) ∧ (r ∈ H → H[r] = (∅)[r])
Used terms: ∅, H