Fizika Tverdogo Tela, 1983 Volume 25, Issue 6,Pages 1620–1626(Mi ftt3781)
Energy spectrum and optical properties of $\mathrm{Ba}_{x}\mathrm{Sr}_{1-x}\mathrm{Nb}_{2}\mathrm{O}_{6}$ and $\mathrm{Ba}_{2}\mathrm{NaNb}_{5}\mathrm{O}_{15}$ in the energy region $0.1$–$35.0$ eV