MLA

Wolff, Helen, 1906-1994. Andreas-Salomé, Lou. Box 77, folder 2197. 1964 Oct 3. https://collections.library.yale.edu/catalog/2017747.

APA, 6th edition

Wolff, Helen, 1906-1994. (["Box 77, folder 2197"])(1964 Oct 3)[Andreas-Salomé, Lou]. https://collections.library.yale.edu/catalog/2017747.