The Blazhko Effect in RR Lyrae stars: Strong observational support for   the oblique pulsator model in three stars
  Using the novel data set of the MACHO project, we show that three ``Blazhko Effect'' RR Lyrae stars show nearly-pure amplitude modulation of a single pulsation mode. This is strong observational evidence that the ``Oblique Pulsator Model'' is the correct solution to this 90-year-old problem. 
The MACHO Collaboration: C. Alcock, D.R. Alves, A. Becker, D.P.   Bennett, K.H. Cook, K.C. Freeman, K. Griest, D.W. Kurtz, M...