APA (7th ed.) Citation

Nikolaus, v. K., & Kallen, G. (1968). Opera omnia. Opera omnia.

Chicago Style (17th ed.) Citation

Nikolaus, von Kues, and Gerhard Kallen. "Opera Omnia." Opera Omnia 1968.

MLA (8th ed.) Citation

Nikolaus, von Kues, and Gerhard Kallen. "Opera Omnia." Opera Omnia, 1968.

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