Equation Icon  -q ′ q- ′ q- ′ α′ ′ tail Φ α(x) = − r2U (x,x )∂αr + r U;α(x,x ) + rU;α′(x, x)u ∂αu + qV(x, x)∂αu + Φα (x), (17.11 )