Khirina, G., and A. Savchenko. “The Story of Three Letters. Spiritual Relay of the Generations. V. N. Karazin – E. I. Koltunovsky – M. F. Sumtsov”. V. N. Karazin Kharkiv National University Bulletin ‘History of Ukraine. Ukrainian Studies: Historical and Philosophical Sciences’, Vol. 35, Dec. 2022, pp. 45-50, doi:10.26565/2227-6505-2022-35-05.