Fragmented information about the war appears in surviving sources, including Völuspá, a poem collected in the Poetic Edda in the 13th century from earlier traditional sources; in the book Skáldskaparmál in the Prose Edda, written in the 13th century by Snorri Sturluson; and in euhemerized form in the Ynglinga saga from Heimskringla, also written by Snorri Sturluson in the 13th century.