“…For r > q + 2, u 1 is determined by the elliptic local problem − ∇ y · S a (y, s) ds · (∇u (x, t) + ∇ y u 1 (x, t, y)) = 0 (18) and since u 1 is independent of s, the coefficient (15) can, in this case, be expressed as b∇u (x, t) = Y S a (y, s) ds (∇u (x, t) + ∇ y u 1 (x, t, y)) dy.…”