1. Groups et Algèbres de Lie;Bourbaki,1972
2. Projective profinite groups;Gruenberg;J. London Math. Soc.,1967
3. A note on SI groups;Hall;J. London Math. Soc.,1964
4. A bound for the derived length of certain polycyclic groups;Humphreys;J. London Math. Soc.,1971
5. General Topology;Kelley,1955