MLA

Clésinger-Sand, Solange, 1828-1899. Aucante, Emile. Box 1, folder 3. 1871-1895, undated. https://collections.library.yale.edu/catalog/17444443.

APA, 6th edition

Clésinger-Sand, Solange, 1828-1899. (["Box 1, folder 3"])(1871-1895, undated)[Aucante, Emile]. https://collections.library.yale.edu/catalog/17444443.