A. Lahmar, S. Ganschow, J. Doerschel, K. Tsuzuku, M. Couzi, and B. Elouadi, “Crystal Growth and Dielectric Study of the Niobate Series K3Sr2RNb10O30 (R = Lanthanide) of Tungsten Bronze Structure”, Eurasian Chem.-Technol. J., vol. 11, no. 1, pp. 1–6, Jan. 2009.