APA (7th ed.) Citation

Willke, H. (1994). Systemtheorie. Systemtheorie.

Chicago Style (17th ed.) Citation

Willke, Helmut. "Systemtheorie." Systemtheorie 1994.

MLA (9th ed.) Citation

Willke, Helmut. "Systemtheorie." Systemtheorie, 1994.

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