MLA

Lindbergh, Charles A. (Charles Augustus), 1902-1974. On hunting trip with Charles August Lindbergh. Box 2, folder 21. Circa 1911. https://collections.library.yale.edu/catalog/10011480.

APA, 6th edition

Lindbergh, Charles A. (Charles Augustus), 1902-1974. (["Box 2, folder 21"])(Circa 1911)[On hunting trip with Charles August Lindbergh]. https://collections.library.yale.edu/catalog/10011480.