Equation Icon  ( ) ∑n 0 I P(∂ ∕∂x) = Bj -∂--+ ( ∑n jk j k ∂2 n∑ j j ∂ ) . (3.57 ) ∂xj (A + B B )∂xj∂xk + (C + DB )∂xj + E D j=1 j,k=1 j=1