Beckmann, P. (1990). A history of PI. New York: Barnes & Noble Books.
Chicago Style aipamenaBeckmann, Petr. A History of PI. New York: Barnes & Noble Books, 1990.
MLA aipamenaBeckmann, Petr. A History of PI. New York: Barnes & Noble Books, 1990.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.