Allen, B. (1996). Sprechspiegel III Lernprogramm. : IBM - International Business Machines Corporation.
Cita Chicago (17th ed.)Allen, Barbara. Sprechspiegel III Lernprogramm. Ireland: : IBM - International Business Machines Corporation, 1996.
Cita MLA (8th ed.)Allen, Barbara. Sprechspiegel III Lernprogramm. : IBM - International Business Machines Corporation, 1996.
Atenció: Aquestes cites poden no estar 100% correctes.