MLA

Stieglitz, Alfred, 1864-1946. Two cabinet card photographs of oil portraits by Fedor Encke, by Encke, Berlin, and Kurtz, NY. Box 133, folder 2537. 1884, n.d.. https://collections.library.yale.edu/catalog/17357455.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 133, folder 2537"])(1884, n.d.)[Two cabinet card photographs of oil portraits by Fedor Encke, by Encke, Berlin, and Kurtz, NY]. https://collections.library.yale.edu/catalog/17357455.