Riggans, W. (1983). Numbers. Westminister.
Chicago Style (17th ed.) ZitazioaRiggans, Walter. Numbers. Philadelphia: Westminister, 1983.
MLA (9th ed.) ZitazioaRiggans, Walter. Numbers. Westminister, 1983.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.