  We prove an estimate for the rank of the intersection of free subgroups in
virtually free groups, which is analogous to the Hanna Neumann inequality for
subgroups in a free group and to the S.V. Ivanov estimate for subgroups in free
products of groups. We also prove a more general estimate for the rank of the
intersection of free subgroups in the fundamental group of a finite graph of
groups with finite edge groups.
