Transit Timing Observations from Kepler: III. Confirmation of 4 Multiple   Planet Systems by a Fourier-Domain Study of Anti-correlated Transit Timing   Variations
  We present a method to confirm the planetary nature of objects in systems with multiple transiting exoplanet candidates. This method involves a Fourier-Domain analysis of the deviations in the transit times from a constant period that result from dynamical interactions within the system. The combination of observed anti-correlations in the transit times and mass constraints from dynamical stability allow us to claim the discovery of four planetary systems Kepler-25, Kepler-26, Kepler-27, and Kepler-28, containing eight planets and one additional planet candidate. 
Jason H. Steffen (1), Daniel C. Fabrycky (2,3), Eric B. Ford (4),   Joshua A. Carter (5,3), Jean-Michel Desert (5), Francois...
astro-ph.EP