  We apply the generalized Lomb-Scargle (LS) periodogram to independently
confirm the claim by Sturrock et al (arXiv:1605.03088) of oscillation at a
frequency of 11/year in the decay rates of $\rm{^{90}Sr/^{90}Y}$ from
measurements at the Physikalisch Technische Bundesanstalt (PTB), which however
has been disputed by Kossert and Nahle (arXiv:1407.2493). For this analysis, we
made two different {\it ansatze} for the errors. For each peak in the LS
periodogram, we evaluate the statistical significance using non-parametric
bootstrap resampling. We find using both of these error models evidence for
~11/year periodicity in the $\rm{^{90}Sr/^{90}Y}$ data for two of the three
samples, but at a lower significance than that claimed by Sturrock et al.
