[1] [1] M. Drescher, M. Hentschel, R. Kienberger, M. Uiberacker, V. Yakovlev, A. Scrinzi, T. Westerwalbesloh, U. Kleineberg, U. Heinzmann, and F. Krausz, Nature 419, 803 (2002).

[2] [2] G. Farkas and C. Toth, Phys. Lett. A 168, 447 (1992).

[3] [3] S. E. Harris, J. J. Macklin, and T. W. Hansch, Opt. Commun. 100, 487 (1993).

[4] [4] P. M. Paul, E. S. Toma, P. Breger, G. Mullot, F. Auge, Ph. Balcou, H. G. Muller, P. Agostini, Science 292, 1689 (2001).

[5] [5] M. Hentschel, R. Kienberger, Ch. Spielmann, G. A. Reider, N. Milosevic, T. Brabec, P. Corkum, U. Heinzmann, M. Drescher, and F. Krausz, Nature 414, 509 (2001).

[6] [6] P. B. Corkum, N. H. Burnett, and M. Y. Ivanov, Opt. Lett. 19, 1870 (1994).

[7] [7] M. Ivanov, P. B. Corkum, T. Zuo, and A. Bandrauk, Phys. Rev. Lett. 74, 2933 (1995).

[8] [8] Ph. Antoine, B. Piraux, D. B. Milosevic, and M. Gajda, Phys. Rev. A 54, R1761 (1996).

[9] [9] V Strelkov, A Zair, O. Tcherbakoff, R. Lopez-Martens, E. Cormier, E. Mevel, and E. Constant, J. Phys. B 38, L161 (2005).

[10] [10] V. T. Platonenko and V. V. Strelkov, J. Opt. Soc. Am. B 16, 435 (1999).

[11] [11] M. Kovaoev, Y. Mairesse, E. Priori, H. Merdji, O. Tcherbakoff, P. Monchicourt, P. Breger, E. Mevel, E. Constant, P. Salieres, B. Carre, and P. Agostini, Eur. Phys. J. D 26, 79 (2003).

[12] [12] K. S. Budil, O. Salieres, M. D. Perry, and A. L'Huillier, Phys. Rev. A 48, R3437 (1993).

[13] [13] P. Dietrich, N. H. Burnett, M. Ivanov, and P. B. Corkum, Phys. Rev. A 50, R3585 (1994).

[14] [14] C. Altucci, Ch. Delfin, L. Roos, M. B. Gaarde, A. L'Huillier, I. Mercer, T. Starczewski, and C.-G. Wahlstrom, Phys. Rev. A 58, 3941 (1998).

[15] [15] O. Tcherbakoff, E. Mevel, D. Descamps, J. Plumridge, and E. Constant, Phys. Rev. A 68, 043804 (2003).

[16] [16] R. Lopez-Martens, J. Mauritsson, P. Johnsson, and A. L'Huillier, Phys. Rev. A 69, 053811 (2004).

[17] [17] N. A. Papadogiannis, G. Nersisyan, E. Goulielmakis, M. Decros, M. Tatarakis, E. Hertz, L. A. A. Nikolopoulos, D. Charalambidis, G. D. Tsakiris, P. Tzallas, and K. Witte, Proc. SPIE 5120, 269 (2003).

[18] [18] Z. Chang, Phys. Rev. A 70, 043802 (2004).

[19] [19] Y. Huo, Z. Zeng, R. Li, and Z. Xu, Opt. Express 13, 9897 (2005).

[20] [20] I. J. Sola, Nature Physics 2, 319 (2006).

[21] [21] V. Strelkov, A. Zair, O. Tcherbakoff, R. Lopez-Martens, E. Cormier, E. Mevel, and E. Constant, Appl. Phys. B 78, 879 (2004).

[22] [22] M. Lewenstein, Ph. Balcou, M. Yu. Ivanov, A. L'Huillier, and P. B. Corkum, Phys. Rev. A 49, 2117 (1994).

[23] [23] R. Li, P. Fan, Z. Xu, Z. Zhang, X. Feng, X. Wang, and P. Lu, J. Opt. (Paris) 25, 143 (1994).