<math> <apply><divergence/> <bvar><ci>x</ci></bvar><bvar><ci>y</ci></bvar><bvar><ci>z</ci></bvar> <vector> <apply><plus/><ci>x</ci><ci>y</ci></apply> <apply><plus/><ci>x</ci><ci>z</ci></apply> <apply><plus/><ci>z</ci><ci>y</ci></apply> </vector> </apply> </math>