1. A. Hoffman, P. J. K. Paterson, S. T. Johnson, et al., Phys. Rev. B 53, 1573 (1996).
2. A. I. Bazhin, G. M. Druzhinin, and V. N. Ryzhov, in Proceedings of the XIII International Conference “Ion-Surface Interaction,” Moscow, 1997, Vol. 2, p. 26.
3. N. Kh. Dzhemilev, I. V. Verevkin, S. E. Maksimov et al., in Proceedings of the International Conference “Emission Electronics,” Tashkent, 1997, p. 135.
4. N. Kh. Dzhemilev, I. V. Verevkin, S. E. Maksimov, et al., Izv. Ross. Akad. Nauk, Ser. Fiz. 60(7), 121 (1996).
5. T. Tada and T. Kanayama, Jpn. J. Appl. Phys. 80, L63 (1996).