Well, the wikipediaWikipedia gives an example of a sylowSylow theorem,, and there is more on this in notes these notes by Igusa.Sylow theorems by Igusa. There is also the following paper of Baer:
Sylow theorems for infinite groupsSylow theorems for infinite groups
Reinhold Baer Source
Source: Duke Math. J. Volume 6, Number 3 (1940), 598-614.