The story of Au Co and the hundred eggs survives because two Vietnamese chronicles, compiled centuries after the events they claim to describe, wrote it down. The fourteenth century Linh Nam Chich Quai, Wonders Plucked from the Dust of Linh Nam, compiled under the Tran dynasty and revised in the fifteenth century under the Le, is the earlier surviving witness, and its account supplied the core material Ngo Si Lien drew on when he wrote the legend into Dai Viet Su Ky Toan Thu, the Complete Annals of Dai Viet, the official fifteenth century history that fixed the story in Vietnam's own historiographical record. Read as a chronicle entry rather than only as myth, the story encodes a specific geographic and ethnic self understanding rather than a simple origin tale: Au Co, a mountain immortal, a tien, and Lac Long Quan, a dragon lord tied to the sea and the lowland waters, represent Vietnam's own two founding landscapes, upland and coast, joined in a single union and then formally separated, fifty sons following their mother to the mountains and fifty following their father to the sea. The couple's eldest son, staying with Au Co and founding the state of Van Lang under the title Hung Vuong, gives the chronicle account its political payoff: a national dynasty's own descent is written as flowing specifically through the highland half of the union the myth describes.