Tull, D. S. (1993). Marketing research (6th ed.). Prentice Hall.
Chicago Style aipamenaTull, Donald S. Marketing Research. 6th ed. New Delhi: Prentice Hall, 1993.
MLA aipamenaTull, Donald S. Marketing Research. 6th ed. Prentice Hall, 1993.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.