Frazier, L., & Mills, R. Northstar: Listening and speaking (3a ed.).
Cita Chicago (17th ed.)Frazier, Laurice, i Robin Mills. Northstar: Listening and Speaking. 3a ed.
Cita MLA (8th ed.)Frazier, Laurice, i Robin Mills. Northstar: Listening and Speaking. 3a ed.
Atenció: Aquestes cites poden no estar 100% correctes.