Jacob Grimm, Teutonic Mythology, 4th ed. tr. James Steven Stallybrass, Volume 1 London: George Bell, 1882, OCLC457311367, note 1, p. 219.
E. O. G. Turville-Petre, Myth and Religion of the North: The Religion of Ancient Scandinavia, History of Religion, London: Weidenfeld and Nicolson, 1964, OCLC3264532, p. 162, note 2, p. 306.