McCombs, D. (2000). Ultima thule. Yale University Press.
Cita Chicago (17th ed.)McCombs, Davis. Ultima Thule. New Haven: Yale University Press, 2000.
Cita MLA (9th ed.)McCombs, Davis. Ultima Thule. Yale University Press, 2000.
Atenció: Aquestes cites poden no estar 100% correctes.