Kopp G. Gabriele & Büttner S. Siegfried. (2009). Planet 1: Arbeitsbuch. Ismaning, Hueber Verlag, 2009.
Cita Chicago (17th ed.)Kopp G. Gabriele i Büttner S. Siegfried. Planet 1: Arbeitsbuch. Ismaning, Hueber Verlag, 2009, 2009.
Cita MLA (9th ed.)Kopp G. Gabriele i Büttner S. Siegfried. Planet 1: Arbeitsbuch. Ismaning, Hueber Verlag, 2009, 2009.
Atenció: Aquestes cites poden no estar 100% correctes.