Sobel, M. A. (1991). Precalculus mathematics (4th.ed.). Prentice Hall.
芝加哥风格引文Sobel, Max A. Precalculus Mathematics. 4th.ed. Englewood Cliffs: Prentice Hall, 1991.
MLA引文Sobel, Max A. Precalculus Mathematics. 4th.ed. Prentice Hall, 1991.
警告：这些引文格式不一定是100％准确.