Gunning, K. (1999). Echinacea in the treatment and prevention of upper respiratory tract infections.
Chicago Style aipamenaGunning, K. Echinacea in the Treatment and Prevention of Upper Respiratory Tract Infections. 1999.
MLA aipamenaGunning, K. Echinacea in the Treatment and Prevention of Upper Respiratory Tract Infections. 1999.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.