The opening line of "Nihonshoki," 'Long, long ago, when the heaven and the earth were not separated yet, and light and darkness were not distinguished...' was derived from 'The heaven and the earth were not separated yet; light and darkness were not distinguished yet; the four seasons were not separated yet; all things were not generated yet....' of a Chinese classic, "Huainanzi" (The Masters/Philosophers of Huainan).
『日本書紀』の冒頭「古（いにしえ）に天地未だ剖（わか）れず、陰陽分れざりしとき......」。は中国の古典の『淮南子』の「天地未だ剖（わか）れず、陰陽未だ判（わか）れず、四時未だ分れず、萬物未だ生ぜず......」によっている。