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From Scott's book Group Theory

$1.7.10.$ (Poincaré) The intersection of a finite number of subgroups of finite index is of finite index.

My question is: Did Poincaré prove the Theorem as stated above or something like that? I mean, was he interested in Group Theory or he proved something which resembles the theorem stated above

I would appreciate any suggestion.

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I know that Poincare introduced the notion of the fundamental group. It stands to reason that he had some interest in group theory. – Isaac Solomon Feb 2 '12 at 7:46
Poincaré was one of the early pioneers of group theory, and especially of using topological and geometric methods to do it (along with Nielsen and Dehn - see "Combinatorial Group Theory" by Lyndon and Schupp). I can see no reason to doubt that this theorem was due to him. – user1729 Feb 2 '12 at 9:53
There are two votes to close this question as "not constructive". This seems to be a perfectly legitimate question in the history of mathematics, maybe phrased in a slightly unfortunate way. – t.b. Sep 10 '12 at 21:56
This question is part of this question (with no answer). I suppose we don't need two versions of the same question open, but the system insists. – Martin Apr 29 '13 at 19:13

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