Wikipedia
Samgungnyusa
Samguk Yusa or Memorabilia of the Three Kingdoms is a collection of legends, folktales and historical accounts relating to the Three Kingdoms of Korea ( Goguryeo, Baekje and Silla), as well as to other periods and states before, during and after the Three Kingdoms period. It is the earliest extant record of the Dangun legend, which records the founding of Gojoseon as the first Korean nation.