MLA

Clésinger-Sand, Solange, 1828-1899. Lami-Sarrazin, R.. Box 1, folder 41. 1890, undated. https://collections.library.yale.edu/catalog/17444474.

APA, 6th edition

Clésinger-Sand, Solange, 1828-1899. (["Box 1, folder 41"])(1890, undated)[Lami-Sarrazin, R.]. https://collections.library.yale.edu/catalog/17444474.