The book’s secret alien races is one of the most controversial documents originating from the period when Russia was dominated by communism.
The first edition of the book was published in 1946 and was designed to inform the secret agents of the various alien races who had visited our planet until that time. As long as the iron curtain Russia resisted valuable information in this book they were enshrined.
Rark is the alien species that mankind has not visited since 720. Perhaps they have lost interest in our adventure planet.