A. E. Siegman (1986). Lasers. University Science Books. pp. 105–108. ISBN978-0-935702-11-8. «resonance-approximation amplitude linewidth frequency Lorentzian real.»
Frederick Emmons Terman (1932). Radio Engineering. McGraw-Hill Book Company. «terman frederick universal.»
Harry F. Olson Music, Physics and Engineering. Dover Publications, 1967, pp. 248–249. "Under very favorable conditions most individuals can obtain tonal characteristics as low as 12 Hz."
