M. Elisa, B. A. Sava, I. C. Vasiliu, E. M. Carstea, I. Feraru, C. Tanaselia, M. Senila, B. Abraham, 2012. Optical and structural characterization of Eu3+, Dy3+, Ho3+ and Tm3+ - doped phosphate glasses. Phys. Chem. Glasses: Eur. J. Glass Sci. Technol. B, 53(5), pp. 219-224, 1753-3562.