APA (7th ed.) Citation

Feil, O., Astor, K. M., & Astor, M. (1950). Ex Libris Karl - Maria Astor.

Chicago Style (17th ed.) Citation

Feil, Otto, Karl M. Astor, and Maria Astor. Ex Libris Karl - Maria Astor. [S. l, 1950.

MLA (9th ed.) Citation

Feil, Otto, et al. Ex Libris Karl - Maria Astor. 1950.

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