Reference:Royer et al. 2004
From Global Warming Art
Royer, Dana L., Robert A. Berner, Isabel P. Montañez, Neil J. Tabor, and David J. Beerling (2004). "CO2 as a primary driver of Phanerozoic climate". GSA Today 14 (3): 4-10.
The following pages on Global Warming Art refer to this reference: