The study of Soviet-American scientific relations during the Cold War is an urgent scientific task. The historiography considered the contacts of the two world powers at the highest scientific level (space exploration, Antarctic exploration, etc.). However, connections between individual scientists or universities, as a rule, did not attract special attention. The article for the first time publishes letters from the personal fund of Professor M. Ya. Syuzyumov (Ural University, Sverdlovsk), which he received from Professor of Byzantine History and Literature at Harvard University I. I. Shevchenko, as well as from librarians of the Center for Byzantine Studies at Harvard University in Dumbarton Oaks Lois Hassler-Smith and Merlin Packard. These archival materials allow us to trace the ways of international book exchange, an important driving force in the development of world Byzantine studies in the 1960s and 1970s. At this time, informal contacts were established between Soviet and American scientists, which allowed, avoiding bureaucratic formalities, to receive the latest scientific literature. The letters published in the article indicate that the correspondence of M. Ya. Syuzyumov with the staff of the Dumbarton Oaks library lasted more than 10 years. The American side received scientific periodicals published in Sverdlovsk, materials of confessions and textbooks, and M. Ya. Syuzyumov received novelties of the American Byzantine literature. The authors of the article managed to identify an error made by the co mpilers of the index Who Was Who at Dumbarton Oaks, 1940-2015. In this edition, it is indicated that Lois Smith and Lois Hassler worked in the library. Meanwhile, the analysis of correspondence of M. Ya. Syuzyumov and his colleagues from the USA and data from the American periodical press prove that we are talking about one person -Lois Hassler-Smith. The results obtained by the authors of the article will be used to create a scientific biography of M. Ya. Syuzyumov, as well as to implement projects for the preservation of cultural heritage and the popularization of scientific knowledge.