MLA

Stieglitz, Alfred, 1864-1946. O'Keeffe and Davidson pruning in orchard. Box 122, folder 2453. [1920]. https://collections.library.yale.edu/catalog/10050253.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 122, folder 2453"])([1920])[O'Keeffe and Davidson pruning in orchard]. https://collections.library.yale.edu/catalog/10050253.