APA (7th ed.) Citation

Ullrich, H., Klante, D., & Röttger, E. (1971). El metal. Bouret.

Chicago Style (17th ed.) Citation

Ullrich, Heinz, Dieter Klante, and Ernst Röttger. El Metal. Paris: Bouret, 1971.

MLA (9th ed.) Citation

Ullrich, Heinz, et al. El Metal. Bouret, 1971.