Cita APA (7th ed.)
Grego, P. (2008). Venus and Mercury, and how to observe them. Springer.
Cita Chicago (17th ed.)
Grego, Peter. Venus and Mercury, and How to Observe Them. New York: Springer, 2008.
Cita MLA (9th ed.)
Grego, Peter. Venus and Mercury, and How to Observe Them. Springer, 2008.
Atenció: Aquestes cites poden no estar 100% correctes.