  Greenlees and Sadofsky showed that the classifying spaces of finite groups
are self-dual with respect to Morava K-theory K(n). Their duality map was
constructed using a transfer map. We generalize their duality map and prove a
K(n)-version of Poincare duality for classifying spaces of orbifolds. By
regarding these classifying spaces as the homotopy types of certain
differentiable stacks, our construction can be viewed as a stack version of
Spanier-Whitehead type construction. Some examples and calculations will be
given at the end.
