Космачов, В. Г., and М. В. Космачова. “Quaternary Volcanic Ash of Kharkiv Region”. Visnyk of V. N. Karazin Kharkiv National University, Series "Geology. Geography. Ecology", no. 49, Dec. 2018, pp. 70-82, doi:10.26565/2410-7360-2018-49-06.