APA (7th ed.) Citation

Willke, H. (1993). Systemtheorie Systemtheorie.

Chicago Style (17th ed.) Citation

Willke, Helmut. "Systemtheorie." Systemtheorie 1993.

MLA (9th ed.) Citation

Willke, Helmut. "Systemtheorie." Systemtheorie, 1993.

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