APA (7th ed.) Citation

Luhmann, N. (1990). Essays on self-reference. Columbia University Press.

Chicago Style (17th ed.) Citation

Luhmann, Niklas. Essays on Self-reference. New York: Columbia University Press, 1990.

MLA (9th ed.) Citation

Luhmann, Niklas. Essays on Self-reference. Columbia University Press, 1990.