A. Avila-García, G. Carbajal-Franco, A. Tiburcio-Silver, E. Barrera-Calva, and E. Andrade-Ibarra, “$\alpha - $Fe$_{2}$O$_{3}$ films grown by the spin-on sol-gel deposition method”, Rev. Mex. Fís., vol. 49, no. 3, pp. 219–0, Jan. 2003.