This idea which was mentioned only very briefly by Poincaré, was elaborated in great detail by Minkowski in an extensive and influential paper in German in 1908 called "The Fundamental Equations for Electromagnetic Processes in Moving Bodies". Minkowski using this formulation restated the then recent theory of relativity of Einstein. In particular by restating the Maxwell equations as a symmetrical set of equations in the four variables combined with redefined vector variables for electromagnetic quantities, he was able to show directly and very simply their invariance under Lorentz transformation. He also made other important contributions and used matrix notation for the first time in this context.