Liu, Zhonghui; Pagani, Mark; Zinniker, David; DeConto, Robert; Huber, Matthew; Brinkhuis, Henk; Shah, Sunita R.; Leckie, R. Mark; Pearson, Ann (2009): Global cooling during the Eocene-Oligocene climate transition. American Association for the Advancement of Science, Washington, DC, United States, Science, 323 (5918), 1187-1190, georefid:2009-040970