Butov, Ilya S. “Evidence of Unidentified «aeroplanes» in Viciebsk Guberniya in 1914–1915: A Look through the Prism of the Era”. Journal of the Belarusian State University. History, no. 3, July 2020, pp. 23-33, https://doi.org/10.33581/2520-6338-2020-3-23-33.