Cita APA (7a ed.)

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

Cita Chicago Style (17a ed.)

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

Cita MLA (9a ed.)

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