APA (7th ed.) Citation

Ludlum, R. (2001). The Sigma protocol. Orion.

Chicago Style (17th ed.) Citation

Ludlum, Robert. The Sigma Protocol. London: Orion, 2001.

MLA (8th ed.) Citation

Ludlum, Robert. The Sigma Protocol. Orion, 2001.

Warning: These citations may not always be 100% accurate.