The harmonic gauge condition in the gravitomagnetic equations
  It has been asserted in the literature that the analogy between the linear and first order slow motion approximation of Einstein equations of General Relativity (gravitomagnetic equations) and the Maxwell-Lorentz equations of electrodynamics breaks down if the gravitational potentials are time dependent.   In this work, we show that this assertion is not correct and it has arisen from an incorrect limit of the usual harmonic gauge condition, which drastically changes the physical content of the gravitomagnetic equations. 
J.-F. Pascual-S\'anchez