P. Petitjean, G. L. Lamb-jr-yan, E. B. Gamble-jr, and K. A. Nelson, univers révélé par les raies dábsorption dans le spectre des quasars Analytical description of ultra-short optical pulse propagation in a resonant medium Impulsive Stimulated Scattering: General Importance in Femto-second Laser Pulse Interactions with Matter and Spectroscopic Applications, Ann. Physique Rev. Mod. J. Chem. Phys, vol.24, issue.83, pp.1-126, 1971.