1. W. E. Moerner, in Topics in Current Physics (Springer, Berlin, 1988), Vol. 44, p. 327.
2. H. Maier, B. M. Kharlamov, and D. Haarer, Tunneling Systems in Amorphous and Crystalline Solids, Ed. by P. Esquinazi (Springer, Berlin, 1988), Chap. 6.
3. M. Berg, C. A. Walsh, L. R. Narasimhan, et al., J. Chem. Phys. 88, 1564 (1988).
4. K. Lazonder, K. Duppen, and D. A. Wiersma, J. Phys. Chem. B 104, 6468 (2000).
5. Yu. G. Vainer, M. A. Kol’chenko, A. V. Naumov, et al., J. Lumin. 86, 265 (2000).