MLA

Kilpatrick, Jack Frederick (1915-1967). Recto: financial list with names and numbers; verso: practice English handwriting. Box 1, folder 7. undated. https://collections.library.yale.edu/catalog/15491317.

APA, 6th edition

Kilpatrick, Jack Frederick (1915-1967). (["Box 1, folder 7"])(undated)[Recto: financial list with names and numbers; verso: practice English handwriting]. https://collections.library.yale.edu/catalog/15491317.