Blog posting "[Below is a full summary, which is 1550 words. If that doesn’t work for you, I’ve written a snappier summary here, which is 550 words, although it skips a lot of the detail."
PNAS Journal Article (V.2 No.10) by Boris V. Schmida, Ulf Büntgenb,c,d, W. Ryan Easterdaya, Christian Ginzlerb, Lars Walløee, Barbara Bramantia, and Nils Chr. Stensetha