Glossary of "Environmental Science: Earth as a Living Planet (2nd ed.)" by Botkin & Keller (1998)
- All the possible wavelengths of electromagnetic energy, considered as a continuous range. The spectrum includes long wavelength (used in radio transmission), infrared, visible, ultraviolet, X rays, and gamma rays.
- 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.