1. Harris, Daniel C., Materials for Infrared Windows and Domes; Properties and Performance, SPIE Press (2001).
2. Silfvast, William Tl, Laser Fundamentals, Cambridge University Press, 1999, pp 4–5.
3. Einstein, Albert, Theorie der Lichterzeugung und Lichtabsorption, Annalen der Physik (ser. 4.), 20, 199–206.
4. http://www.nobelprize.org/nobelprizes/physics/laureates/1964/townes-bio.html Last accessed 2/25/2015.
5. The Maser—New Type of Microwave Amplifier, Frequency Standard, and Spectrometer