| ∀ lref. lref ∈ q.lebrefs ↔ (∃ n. eq-entry(n, lref) ∈ q) ∧ lref ≠ none, eq-entry(n, lref) = eq-entry(m, lref0) ∨ eq-entry(n, lref) ∈ q ⊦ lref = none, lref ∈ q.lebrefs, lref ∈ (lref0 ≠ none ⊃ ∅ ++ lref0;∅) |
∀ lref. lref ∈ q.lebrefs ↔ (∃ n. eq-entry(n, lref) ∈ q) ∧ lref ≠ none, eq-entry(n, lref) = eq-entry(m, lref0) ∨ eq-entry(n, lref) ∈ q ⊦ lref = none, lref0 = none, lref ∈ q.lebrefs, lref ∈ ∅ ++ lref0
lref0 = none, ∀ lref. lref ∈ q.lebrefs ↔ (∃ n. eq-entry(n, lref) ∈ q) ∧ lref ≠ none, eq-entry(n, lref) = eq-entry(m, lref0) ∨ eq-entry(n, lref) ∈ q ⊦ lref = none, lref ∈ q.lebrefs, lref ∈ ∅