On the equivalence of G-weak and -strong cores in the marriage problem

In the marriage problem (two-sided one-to-one matching problem), it is well-known that the weak core, the strong core and the set of stable matchings are all equivalent. This paper generalizes the above observation considering the G-weak core and the G-strong core. These are core concepts in which blocking power is restricted to the coalitions belonging to the prescribed class of coalitions G. I give a necessary and sufficient condition that G should satisfy for the equivalence of the G-weak core and the G-strong core.