“…Thus we know that x > 10 and y < 9 constitute the generator of i ∧ m, which together imply that y ≥ 5. Inspection of Figure 10 shows that this describes the elements i, j, and m. The node (16,8,12) = l ∧ m ∧ o covers only the single node (15,8,12). If ¬(x ≤ 15), then because (16,8,12) is closed we must have y ≥ 8 and y ≤ 12), or more compactly, (x > 15) → (8 ≤ y ≤ 12).…”