Brooke, H., & Helen Brooke. (1999). U.F.O.S. Oxford Bookworms Factfiles: Oxford University Press.
Chicago Style CitationBrooke, Helen, i Helen Brooke. U.F.O.S. Oxford Bookworms Factfiles: Oxford University Press, 1999.
Cita MLABrooke, Helen, i Helen Brooke. U.F.O.S. Oxford Bookworms Factfiles: Oxford University Press, 1999.
Atenció: Aquestes cites poden no estar 100% correctes.