"Big Soviet Encyclopedia" (EU) is a huge interpretative and illustrative edition, which became one of the most voluminous and authoritative encyclopedias in the Soviet Union. The first edition of the Encyclopedia was published in 1926, and later it was published in many reprints. While the last edition was published in 1990. In this encyclopedia there was an interface of more than 100 thousand articles from various fields of knowledge, leading scientists, illustrations, cartographic materials and other sources of information. The EU had an invaluable cultural and scientific contribution and was considered a mandatory source of knowledge for every Soviet citizen. It is known that the editors of the Big Russian Encyclopedia carried out active work on modernizing and expanding the materials, covering important events, historical facts and scientific discoveries. Undoubtedly, the Encyclopedia is an important source of information for both students and scientists, as well as for a wide range of readers."