MLA

Kilpatrick, Jack Frederick (1915-1967). Recto: unidentified text; Verso: form bill from United Sew-Vac center, McKinney, Texas, to Mrs. Minnie Jumper in Welling, Oklahoma. Box 23, folder 1875. undated. https://collections.library.yale.edu/catalog/16056923.

APA, 6th edition

Kilpatrick, Jack Frederick (1915-1967). (["Box 23, folder 1875"])(undated)[Recto: unidentified text; Verso: form bill from United Sew-Vac center, McKinney, Texas, to Mrs. Minnie Jumper in Welling, Oklahoma]. https://collections.library.yale.edu/catalog/16056923.