Motivic Galois groups of 1-motives: a survey Seminar on algebraic geometry at Bois Marie 1962-64. Group schemes (SGA 3). Vol. III: Structure of reductive group schemes. Directed by M. Damazure and A. Grothendieck with the collaboration of M. Artin, J.-E. Bertin, P. Gabriel, M. Raynaud and J.-P. Serre 