The written works of Korean literature appeared around the 1st century BC. Before that, ancient myths, legends and oral songs had been circulated. Its primitive artistic activities can be found in China's "Historical Records", "Hanshu", "Three Kingdoms" and North Korea's "Historical Records of the Three Kingdoms" and "Relics of the Three Kingdoms" and other history books. The content is generally the same as the celebration activities for sacrifices and agricultural work. The combination reflects the production activities and original religious beliefs of ancient people. The oldest existing four-character poems "Honghou Yin" and "Welcoming God Song" may be oral ballads recorded using written words. "Honghou Yin" comes from the Yuefu of Han Dynasty in China. According to the description of Cui Bao from the Western Jin Dynasty in "Gujinzhu", it is believed to be written by ancient Koreans. The oldest myth and legend in Korea, represented by "The Myth of Tangun", tells the story of the god Tangun who established the ancient Joseon Kingdom. After the introduction of Chinese language into Korea, written literature began. For nearly two thousand years, they have borrowed Chinese characters to write official documents, write books and create literature. In 1444, Hangeul was created during the reign of King Sejong of the Lee Dynasty, and Mandarin literature became increasingly popular. By the end of the Lee Dynasty, Chinese literature began to decline and was finally replaced by Mandarin literature. Korean literature is divided into the following 4 periods.