Cita APA (7th ed.)

Ludlum, R. (2001). The Sigma protocol. St. Martin's Press.

Cita Chicago (17th ed.)

Ludlum, Robert. The Sigma Protocol. New York: St. Martin's Press, 2001.

Cita MLA (9th ed.)

Ludlum, Robert. The Sigma Protocol. St. Martin's Press, 2001.