Epistolary materials of the collections of the Russian Academy of Sciences (St. Petersburg branch of the Archive of the Russian Academy of Sciences, "Archive of Orientalists" of the Institute of Oriental Manuscripts of the Russian Academy of Sciences) and the Turfan collection of the Museum of Asian Art (Berlin): correspondence of expedition participants - Russian (M.M. Berezovsky, S.M. Dudin, D.A. Klemenz, P.K. Kozlov, S.E. Malov, S.F. Oldenburg), German (A. Grünwedel, F. von Le Kock, G. Hut) and English (M.A. Stein), representatives of the diplomatic corps (A.A. Dyakov, S.A. Kolokolov, N.N. Krotkov, N.F. Petrovsky, V.M. Uspensky, J. Macartney) and the scientific world (G. Buhler, R. Pichel, V.V. Radlov, V.R. Rosen).