 A number of solution concepts have been introduced for coalitional games (see for instance Osborne &amp; Rubinstein 1994, and Apt 2009 (Other Internet Resources)).  For the present purposes we are only going to discuss what is possibly the best-known: the core. The core is a collection of stable outcomes, i.e., outcomes for which no coalition exists whose members are both able and willing to deviate from it. It can be seen as the set of outcomes to which there is no effective opposition (Abdou &amp; Keiding 1991).