. A direct proof for this statement is immediate. To find the difference Le, —Lei, one simply needs to integrate: S„A(ei,e0 + A(ei,q) — A(q, ei) — A(ej, ej) — A(ei, + A(q, ej) dq (6.48) We note that: A(ei,ei) = nu, 11(ei,(1) = Ek qkaik and A(q,ei) = Ek qkakil where tie = 1 — — All these functio