Oppenheim, A. V., Willsky, A. S., Nawab, S. H., Willsky, A. S., Nawab, S. H., Willsky, A. S., & Nawab, H. S. (1997). Signals and systems (2nd ed.). Englewood Cliffs, NJ.: Prentice-Hall.

Oppenheim, Alan V., Alan S. Willsky, S. Hamid Nawab, Alan S. Willsky, Syed Hamid Nawab, Allan S. Willsky, and Hamid S. Nawab. Signals and Systems. 2nd ed. Englewood Cliffs, NJ.: Prentice-Hall, 1997.

Oppenheim, Alan V., et al. Signals and Systems. 2nd ed. Englewood Cliffs, NJ.: Prentice-Hall, 1997.