| ⊦ q1.lebrefs ⊆ q0.lebrefs ++ (v × m) ∧ abs(avols, apebs, vols, q0) ∧ v ∈ avols ∧ m < # avols[v] ∧ avols[v][m] ≠ erased → abs(avols, apebs, vols, q1) |
m < # avols[v], abs(avols, apebs, vols, q0), v ∈ avols, q1.lebrefs ⊆ q0.lebrefs ++ (v × m) ⊦ avols[v][m] = erased, abs(avols, apebs, vols, q1)