How to retrieve common data in Sql Server 2005?

 Hi,
There are G1, G2, G3 groups in GROUPS TABLE
and P1, P2, P3, P4, P5 properties in PROPERTIES TABLE. Now in GPMAPPING table
G1 has P1, P2, P3 properties
G2 has p1, p2, p3, p4 properties and
G3 has p1, p5 properties

I want the common properties of G1, G2, G3 groups i.e., output as P1.

Thanks in advance