1. P. Hall, A note on soluble groups, J. London Math. Soc. 3 (1928), 98.
2. \bysame, A characteristic property of soluble groups, J. London Math. Soc. 12 (1937), 198.
3. \bysame, On the Sylow systems of a soluble group, Proc. London Math. Soc. 43 (1937), 316.
4. L. Pontrjagin, Topological groups, Chapter III, pp. 77-80, Princeton Univ. Press, Princeton, N. J., 1939.
5. Séminaire Bourbaki 1959/60, No. 189, Cohomologie des groupes compacts totalement discontinus: A. Douady, from notes by S. Lang on an unpublished article by J. Tate.