Cita APA (7th ed.)
Sobel, M. A. (1991). Precalculus mathematics (4th.ed.). Prentice Hall.
Cita Chicago (17th ed.)
Sobel, Max A. Precalculus Mathematics. 4th.ed. Englewood Cliffs: Prentice Hall, 1991.
Cita MLA (9th ed.)
Sobel, Max A. Precalculus Mathematics. 4th.ed. Prentice Hall, 1991.
Atenció: Aquestes cites poden no estar 100% correctes.