MLA

Wolff, Kurt, 1887-1963. Correspondence. Box 7, folder 265-71. 1913-35, n.d.. https://collections.library.yale.edu/catalog/2021360.

APA, 6th edition

Wolff, Kurt, 1887-1963. (["Box 7, folder 265-71"])(1913-35, n.d.)[Correspondence]. https://collections.library.yale.edu/catalog/2021360.