APA (7th ed.) Zitazioa
Piper, J. (2007). Don't waste your time. Crossway Books.
Chicago Style (17th ed.) Zitazioa
Piper, John. Don't Waste Your Time. Wheaton, Ill.: Crossway Books, 2007.
MLA (9th ed.) Zitazioa
Piper, John. Don't Waste Your Time. Crossway Books, 2007.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.