Grava, S. (2003). Urban transportation systems. New York: McGraw-Hill.
Chicago Style aipamenaGrava, Sigurd. Urban Transportation Systems. New York: McGraw-Hill, 2003.
MLA aipamenaGrava, Sigurd. Urban Transportation Systems. New York: McGraw-Hill, 2003.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.