1. R.Y. Chiao, E. Garmire, C.H. Townes, Phys. Rev. Lett. 13, 479 (1964).
2. V.I. Talanov, Izvestia V.U.Z. Radiofyzika (U.S.S.R.) 7, 564 (1964).
3. G.A. Askar’yan, Zh. Eksp. Teor. Fiz. 42, 1567 (1962) [Soy. Phys. JETP 15, 1088 ].
4. R.Y. Chiao, PhD thesis, Massachusetts Institute of Technology, 1965.
5. P.L. Kelley, Phys. Rev. Lett. 15, 1005 (1965).