Two methods for the light curves extrema determination
  Two methods for the determination of extrema timings and their uncertainties appropriate for the analysis of time series of variable stars using matrix calculus are presented. The method I is suitable for determination of times of extrema of non-periodical variables or objects, whose light curves vary. The method II is apt for O-C analyses of objects whose light curves are more or less repeating. 
Zdenek Mikulasek and Tomas Graf
astro-ph.IM physics.data-an