The history of mining rough diamonds in Russia dates back to the 18th century, but sustained exploration began in the late 1930s. This was when Russian researcher Vladimir Sobolev published his paper on the geological similarities between South Africa and Siberia. Activity was interrupted by the Great Patriotic War (World War II), but resumed in the late 1940s. Geological expeditions were sent out to find rough diamond deposits around the river Vilyui, and its tributaries – the Malaya (small) Botuobia, and Bolshaya (big) Botuobia. In 1949 they found the first rough diamond in Yakutia. By 1954, the Zarnitsa pipe was discovered – the first primary diamond deposit in the Soviet Union. From that point, Russian diamonds made their way into world markets.