MLA

Bemelmans, Ludwig, 1898-1962. Letters. Box 1 | Folder 1. https://collections.library.yale.edu/catalog/15510532.

APA, 6th edition

Bemelmans, Ludwig, 1898-1962. (["Box 1 | Folder 1"])[Letters]. https://collections.library.yale.edu/catalog/15510532.