APA (7th ed.) Citation

Héroux, B., & Schmidt-Hell, M. (1907). Ex-libris Marie Hell.

Chicago Style (17th ed.) Citation

Héroux, Bruno, and Maria Schmidt-Hell. Ex-libris Marie Hell. [S. l, 1907.

MLA (9th ed.) Citation

Héroux, Bruno, and Maria Schmidt-Hell. Ex-libris Marie Hell. 1907.

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