MLA

Koch, Frederick R. (Frederick Robinson). Hahn, Reynaldo. Box 48, folder 998. [ca. 1906]-[ca. 1912], n.d.. https://collections.library.yale.edu/catalog/12156605.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 48, folder 998"])([ca. 1906]-[ca. 1912], n.d.)[Hahn, Reynaldo]. https://collections.library.yale.edu/catalog/12156605.