References
Auslander, L.: Simply transitive groups of affine motions. Am. J. Math.99, 809–821 (1977)
Borel, A.: Linear algebraic groups. 2nd ed. Berlin Heidelberg New York Tokyo: Springer 1991
Goldman, W.M., Hirsch, M.W.: Affine manifolds and orbits of algebraic groups. Trans. Am. Math. Soc.295, 175–198 (1986)
Grunewald, F., Segal, D.: On affine crystallographic groups. (To appear)
Helmstetter, J.: Radical d'une algèbre symétrique à gauche. Ann. Inst. Fourier, Grenoble29, 17–35 (1979)
Helmstetter, J.: Radical et groupe formel d'une algèbre symétrique à gauche. Thèse de doctorat 3e cycle. Université de Grenoble (1975)
Kim, H.: Complete left-invariant affine structures on nilpotent Lie groups. J. Differ. Geom.24, 373–394 (1986)
Milnor, J.: On fundamental groups of complete affinely flat manifolds. Adv. Math.25, 178–187 (1977)
Medina Perea, A.: Flat left-invariant connections adapted to the automorphism structure of a Lie group. J. Differ. Geom.16, 445–474 (1981)