APA (7th ed.) Citation

Willke, H., & Willke, H. (1993). Systemtheorie Systemtheorie.

Chicago Style (17th ed.) Citation

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

MLA (8th ed.) Citation

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

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