Glossary of "The Evolution of Plants (2nd ed.)" by Willis & McElwain (2014)
- Atmospheric trace gas that has a strong greenhouse influence.
Glossary of "Environmental Science: Earth as a Living Planet (2nd ed.)" by Botkin & Keller (1998)
- Molecule of carbon and hydrogen, which is a naturally occurring gas in the atmosphere. One of the so-called greenhouse gases.
- Botkin, D. B. & Keller, E. A. 1998. Environmental Science: Earth as a Living Planet, 2nd ed. -xxxxii + 649 pp. John Wiley & Sons, Inc., New York.
- Willis, K. J. & McElwain, J. C. 2014. The Evolution of Plants, 2nd ed. -ix + 398 pp. Oxford University Press, Oxford.