  We prove that the {\em gauge dependent} gluon spin, gluon and quark orbital
angular momenta operators have {\em gauge invariant} expectation values on
hadron states with {\em definite} momentum and polarization, therefore the
conventional decomposition of nucleon spin into contributions from the spin and
orbital angular momentum of quark and gluon is {\em gauge independent}. Similar
conclusions apply to the {\em gauge dependent} quark momentum and kinetic
energy operators, and accordingly nucleon momentum and mass structures.
