1. P. M. W. French, J. A. R. Williams and J. R. Taylor, Opt. Lett. 14, 686 (1989).
2. J. Goodberlet, J. Wang, J. G. Fujimoto and P. A. Schulz, Opt. Lett. 14, 1125 (1989).
3. N. Sarukura, Y. Ishida, H. Nakano and Y. Yamamoto, Appl. Phys. Lett. 56, 814 (1989), Y. Ishida, N. Sarukura and H. Nakano, in Digest of Meeting on Ultrafast Phenomena (1990), postdeadline paper PD11, and N. Sarukura, Y. Ishida and H. Nakano, in Digest of Conference on Lasers and Electro-Optics (1990), paper CWF12.
4. U. Keller, W. H. Knox and H. Roskos, in Digest of Meeting on Ultrafast Phenomena (1990), postdeadline paper PD9.
5. J. Squier, F. Salin, C. Rouyer, S. Coe and G. Mourou, in Digest of Conference on Lasers and Electro-Optics (1990), postdeadline paper CPDP9.