1. D. Strickland, G. Mourou, Opt. Commun. 56, 219 (1985)
2. W.T. Hill, C.H. Lee, Light-Matter Interaction: Atoms and Molecules in External Fields and Nonlinear Optics (WILEY-VCH, Weinheim, 2007). ISBN 978-3-827-40661-6
3. F.H. Faisal, Theory of Multiphoton Processes (Plenum, New York, NY, 1987). ISBN 0-306-42317
4. L.V. Keldysh, Sov. Phys. JETP 20, 1307 (1965)
5. A.M. Perelomov, V.S. Popov, M.V. Terent’ev, Sov. Phys. JETP 23, 924 (1966)