van Haasteren described in more detail today how they can recognize that covariances in pulsar timing residuals among multiple pulsars can be the result of a stochastic background of gravitational radiation. The method they use is a Gaussian process, which is a technology much loved by Bovy, myself, and our collaborators (and at least one of my regular readers). The nice thing is that van Haasteren's project is precisely a Gaussian process, and he knows that for good physical reasons. Furthermore, the covariance matrix he constructs is highly constrained by the physics of the problem. At lunch, he described to a subset of Camp Hogg some of the issues he faces in the real world; two of the most interesting are linear algebra—he needs to invert and take the determinant of some very large, very non-sparse matrices—and visualization—if you detect a signal at low signal-to-noise ratio, how do you convince the skeptics? Camp Hogg didn't have much useful to give him on either issue, though we can help, I think, with sampling issues.