1. A.E. Siegman, Lasers (University Science Books, Mill Valley, CA, 1986), pp. 746–747
2. W. Koechner, Solid-State Laser Engineering, 5th. rev. edn. (Springer, Berlin, 1999), pp. 469–473
3. See the ISO standards 11146-1, Lasers and laser-related equipment-test methods for laser beam widths, divergence angle and beam propagation factor – Part 1: stigmatic and simple astigmatic beams and 11146-3 Lasers and laser-related equipment-test methods for laser beam widths, divergence angle and beam propagation factor – Part 3: Alternative test methods and geometrical laser beam classification and propagation
4. M. Ciofini, E. Favilla, A. Lapucci, E. Sani, Opt. Laser Technol. 39, 1380 (2007)
5. W. Koechner, Solid-State Laser Engineering, 5th. rev. edn. (Springer, Berlin, 1999), pp. 152–176