1. L.C. Thompson, in K.A. Gshneider and L. Eyring (eds.), Handbook on the Physics and Chemistry of Rare Earths, North Holland, Amsterdam, 1979, p. 212.
2. J.-C. Bunzli, in G.R. Choppin and J.-C. Bunzli (eds.), Lanthanide Probes in Life, Medical and Environmental Science, Elsevier, Amsterdam, 1989.
3. B. Alpha, R. Ballardini, V. Balzani, J.-M. Lehn, S. Perathoner and N. Sabbatini, Photochem. Photobiol., 52 (1990) 299.
4. (a) M. Pietraszkiewicz, J. Karpink and A.K. Rout, Pure Appl. Chem., 65 (1993) 563;
5. (b) G.F. de Sá, W.M. de Azevedo and A.S.L. Gomes, J. Chem. Res. (S), (1994) 234.