V. D. Sedykh, O. G. Rybchenko, E. V. Suvorov, A. I. Ivanov, V. I. Kulakov, “Oxygen vacancies and valence states of iron in SrFeO$_{3-\delta}$ compounds”, Phys. Solid State, 62:10 (2020), 1916–1923
N. V. Barkovskii, “Identification of Fe (IV) in oxides by chemical test methods”, Zavod. lab., Diagn. mater., 86:6 (2020), 5