We give the sketch of a combinatorial proof of the construction by Gromov of a group whose Cayley graph contains a family of expanders. Combining the methods in [Oll1] and [Oll2], it is possible to give a proof of the construction invented by M. Gromov in [G] that there is an infinite group whose Cayley graph contains (in some quasi-isometric sense) a family of expanders. We only give the main ...
