MLA

Kilpatrick, Jack Frederick (1915-1967). Practice handwriting. Box 1, folder 72. undated. https://collections.library.yale.edu/catalog/15492073.

APA, 6th edition

Kilpatrick, Jack Frederick (1915-1967). (["Box 1, folder 72"])(undated)[Practice handwriting]. https://collections.library.yale.edu/catalog/15492073.