Existence of positive harmonic functions on groups and on covering manifolds Philippe Bougerol, Laure Elie (1995) Annales de l'I.H.P. Probabilités et statistiques
Expansion and random walks in SL d ( ℤ / p n ℤ ) : I Jean Bourgain, Alex Gamburd (2008) Journal of the European Mathematical Society We prove that the Cayley graphs of SL d ( ℤ / p n ℤ ) are expanders with respect to the projection of any fixed elements in SL d ( ℤ ) generating a Zariski dense subgroup.
Expansion and random walks in SL d ( ℤ / p n ℤ ) : II Jean Bourgain, Alex Gamburd (2009) Journal of the European Mathematical Society
Exposants critiques pour le mouvement brownien et les marches aléatoires Jean-François Le Gall (1999/2000) Séminaire Bourbaki