 According to the Korean view, these refer to today's Liancourt Rocks, while the Japanese researchers of these documents have stated that the various references to Usan-do refer at different times to Jukdo, its neighboring island Ulleungdo, or a non-existent island between Ulleungdo and Korea.Researchers disagree on who first had administrative control over the islets due to ambiguities in early historical records and maps, partly due to changes in the names of the islands in the area over the years.Samguk Sagi ("History of Three Kingdoms") recorded that in 512, the 13th reign year of King Jijeung of Silla, one of the Three Kingdoms of Korea, General Kim Isabu conquered Usan, whence it submitted yearly tributes to the Silla court.