  We derive Bell inequalities for graph states by generalizing the approach
proposed by Ardehali [Phys. Rev. A 46, 5375 (1992)] for
Greenberger-Horne-Zeilinger (GHZ) states. Using this method, we demonstrate
that Bell inequalities with nonstabilizer observables are often superior to the
optimal GHZ-Mermin-type (or stabilizer-type) Bell inequalities.
