Period Determination of RR Lyrae Stars
  The classic problem of detection of periodic signals in the presence of noise becomes much more challenging if the observation times are themselves periodic, contain large gaps, or consist of data from several different instruments. For RR Lyrae light curves the additional attribute of highly non-sinusoidal variation adds another dimension. This memo discusses and contrasts Discrete Fourier, Periodogram, and Phase Dispersion Minimization (PDM) analysis techniques. A new version of the PDM technique is described with tests and applications. 
Robert F. Stellingwerf (Stellingwerf Consulting, Huntsville, Alabama)
astro-ph.SR