Leslie, Andrew B., Jeremy M. Beaulieu, Hardeep S. Rai, Peter R. Crane, Michael J. Donoghue, and Sarah Mathews. 2012. Hemisphere-scale differences in conifer evolutionary dynamics. Proceedings of the National Academy of Sciences 109(40):16217-16221. Available (2016.02.15). Be sure to download the "supplemental information" as well.