Matías Alvarado PhD CINVESTAV   Av. Instituto Politécnico Nacional 2508 Col. San Pedro Zacatenco Mexico, DF 07360 México   matias@cs.cinvestav.mx   http://www.cs.cinvestav.mx/investigadores/Ematias           JEL Areas: C6 : Mathematical Methods and Programming: General C7 : Game Theory and Bargaining Theory:General