APA (7th ed.) Zitazioa
Callihan, D. (2009). National Wildlife Refuge System. Nova Science Publishers.
Chicago Style (17th ed.) Zitazioa
Callihan, David. National Wildlife Refuge System. New York: Nova Science Publishers, 2009.
MLA (9th ed.) Zitazioa
Callihan, David. National Wildlife Refuge System. Nova Science Publishers, 2009.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.