1. Gorokhovskii AA, Kaarli RK, Rebane LA (1974) JETP Lett 20: 216
2. Kharlamov BM, Personov RI, Bykovskaya LA (1974) Opt Commun 12: 191
3. Friedrich J, Haarer D (1984) Angew Chemie 23: 113
4. Moerner WE (ed) (1988) Persistent spectral hole-burning: science and applications. Springer, Berlin Heidelberg New York
5. Horie K, Furusawa A (1992) In: Rabek JF (ed) Progress in photochemistry and photo-physics. CRC Press, Boca Raton, vol 5, chap 2