I want to calculate the divergence of a two dimensional 3 order tensor; e.g. nabla=(d/dx, d/dy) and Ax = ( C D) ( E F), Ay = ( G H) ( I J) (it's a 2x2x2 cube). Index notation: (nabla)_i = d/dx_i and elements of A are A_ijk How do I contract it properly to calculate Divergence of A (Nabla inner product A)? Thanks a lot!!