APA-viite (7. p.)

Friedrichs, K. O. (1961). Spectral theory of operators in Hilbert Space. New York University.

Chicago-viite (17. p.)

Friedrichs, K. O. Spectral Theory of Operators in Hilbert Space. Nueva York: New York University, 1961.

MLA-viite (9. p.)

Friedrichs, K. O. Spectral Theory of Operators in Hilbert Space. New York University, 1961.