Yu. V. Nikol'skii, B. A. Maksimov, Yu. N. Dem’yanets, V. V. Ilyukhin, N. V. Belov, “Crystal structure of synthetic rare-earth germinate $\mathrm{Sm}_4\mathrm{Ge}_3\mathrm{O}_9(\mathrm{OH})_6=\mathrm{Sm}_4[\mathrm{Ge}^{\mathrm{VI}}\mathrm{Ge}^{\mathrm{IV}}_2\mathrm{O}_9](\mathrm{OH})_6$”, Dokl. Akad. Nauk SSSR, 233:3 (1977), 362–365
