APA (7th ed.) Citation

Halmos, P. R. (1967). A Hilbert space problem book. American Book Co..

Chicago Style (17th ed.) Citation

Halmos, Paul R. A Hilbert Space Problem Book. New York: American Book Co., 1967.

MLA (9th ed.) Citation

Halmos, Paul R. A Hilbert Space Problem Book. American Book Co., 1967.