1. N. R. Isenor, V. Merchant, R. S. Hallsworth andM. C. Richardson:Can. J. Phys.,51, 1281 (1973).
2. R. V. Ambartzumian, N. V. Chekalin, V. S. Doljikov, V. S. Letokhov andE. A. Ryabov:Chem. Phys. Lett.,25, 515 (1974).
3. R. V. Ambartzumian, V. S. Letokhov, E. A. Ryabov andN. V. Chekalin:Ž. Eksp. Teor. Fiz. Pis’ma Red.,20, 597 (1974) (English translation:JETP Lett.,20, 273 (1974).
4. R. V. Ambartzumian Yu. A. Gorokhov, V. S. Letokhov andG. N. Makarov:Ž. Ėksp. Teor. Fiz. Pis’ma Red.,21, 375 (1975) (English translation:JETP Lett.,21, 171 (1975)).
5. An excellent and almost complete review of both theoretical and experimental works isR. V. Ambartzumian andV. S. Letokhov: inChemical and Biochemical applications of lasers, Vol.3, edited byC. B. Moore (New York, N. Y., 1977), p. 167.