Citation: Biryukov, Yaroslav P.; Zinnatullin, Almaz L.; Bubnova, Rimma S.; Vagizov, Farit G.; Shablinskii, Andrey P.; Filatov, Stanislav K.; Shilovskikh, Vladimir V.; Pekov, Igor V. (2020). Investigation of thermal behavior of mixed-valent iron borates vonsenite and hulsite containing [OM~4~]^n^^+^ and [OM~5~]^n^^+^ oxocentred polyhedra by in situ high-temperature M\"ossbauer spectroscopy, X-ray diffraction and thermal analysis. Acta Crystallographica Section B, 76, pp. 543-553.