Boyko, P.S., Albekov, A.Y. and Reznikova, O.G. 2020. Petrographic characteristics of the granite gneisses of the Usmanskiy Pinewood forest: towards the origin of the “Kudeyarov stones” in the Voronezh State Nature Biosphere Reserve. Proceedings of Voronezh State University. Series: Geology. 4 (Dec. 2020), 87-93. DOI:https://doi.org/10.17308/geology.2020.4/3131.