| lref ∈ q.lebrefs ∪ (lref0 ≠ none ⊃ ∅ ++ lref0;∅), ∀ lref. lref ∈ q.lebrefs ↔ (∃ n. eq-entry(n, lref) ∈ q) ∧ lref ≠ none ⊦ #(q.lebrefs ∪ (lref0 ≠ none ⊃ ∅ ++ lref0;∅)) = 0, q.lebrefs ∪ (lref0 ≠ none ⊃ ∅ ++ lref0;∅) = ∅, (∃ n. eq-entry(n, lref) = eq-entry(m, lref0) ∨ eq-entry(n, lref) ∈ q) ∧ lref ≠ none |
lref ∈ q.lebrefs ∪ (lref0 ≠ none ⊃ ∅ ++ lref0;∅), ∀ lref. lref ∈ q.lebrefs ↔ (∃ n. eq-entry(n, lref) ∈ q) ∧ lref ≠ none ⊦ #(q.lebrefs ∪ (lref0 ≠ none ⊃ ∅ ++ lref0;∅)) = 0, lref0 = none, q.lebrefs ∪ (∅ ++ lref0) = ∅, (∃ n. eq-entry(n, lref) = eq-entry(m, lref0) ∨ eq-entry(n, lref) ∈ q) ∧ lref ≠ none
lref0 = none, lref ∈ q.lebrefs ∪ (lref0 ≠ none ⊃ ∅ ++ lref0;∅), ∀ lref. lref ∈ q.lebrefs ↔ (∃ n. eq-entry(n, lref) ∈ q) ∧ lref ≠ none ⊦ #(q.lebrefs ∪ (lref0 ≠ none ⊃ ∅ ++ lref0;∅)) = 0, q.lebrefs ∪ ∅ = ∅, (∃ n. eq-entry(n, lref) = eq-entry(m, lref0) ∨ eq-entry(n, lref) ∈ q) ∧ lref ≠ none