Renson1 developed a string method for period analysis, which proposes a better distribution of the trial periods, by taking into account the observational error, for determining a criterium to select the right period. The advantage of the method is most obvious when the amount of observations is very low. 

The Renson dialog box is similar to the Lomb-Scargle dialog box, except for the presence of the Observational mag error field in the Additional parameters section, which allows to input the observational error to be used by the Renson method. Prominent periods of the Period Window appear as valleys.

(1) Renson, P., 1978, A&A., 63, 125