S. V. Shekhovtsov, N. O. Mchedlov-Petrossyan, N. N. Kamneva, and T. Y. Gromovoy, “New orange dyes: nitroderivatives of sulfonefluorescein”, Khark. Univ. Bull. Chem. Ser., no. 24, pp. 7-18, Oct. 2014.