  Robertson et al.(Reports, July 25 2014, p440-444)(1) claimed that
activity-induced variability is responsible for the Doppler signal of the
proposed planet candidate GJ 581d. We point out that their analysis using
periodograms of residual data is incorrect, further promoting inadequate tools.
Since the claim challenges the viability of the method to detect exo-Earths, we
urge for more appropriate analyses (see appendix).
