MLA

Clésinger-Sand, Solange, 1828-1899. Calmann, Paul. Box 1, folder 14. 1894 June 21. https://collections.library.yale.edu/catalog/17444453.

APA, 6th edition

Clésinger-Sand, Solange, 1828-1899. (["Box 1, folder 14"])(1894 June 21)[Calmann, Paul]. https://collections.library.yale.edu/catalog/17444453.