Ekart, D. D., Cerling, T. E., Montanez, I. P., & Tabor, N. J. (1999). A 400 million year carbon isotope record of pedogenic carbonate; implications for paleoatomospheric carbon dioxide.
American Journal of Science,
299(10), 805–827.
https://doi.org/10.2475/ajs.299.10.805