Loulergue, Laetitia, Adrian Schilt, Renato Spahni, Valérie Masson-Delmotte, Thomas Blunier, Bénédicte Lemieux, Jean-Marc Barnola, Dominique Raynaud, Thomas F. Stocker, and Jérôme Chappellaz. Orbital and millennial-scale features of atmospheric CH4 over the past 800,000 years. Nature 453, no. 7193 (2008): 383-386.