MLA

Johnston, William Walker Whitehall, 1835-1886. Album Page 6. Recto, left: Portrait of William Walker Whitehall Johnston. Box 1, folder 4. circa 1860. https://collections.library.yale.edu/catalog/16657578.

APA, 6th edition

Johnston, William Walker Whitehall, 1835-1886. (["Box 1, folder 4"])(circa 1860)[Album Page 6. Recto, left: Portrait of William Walker Whitehall Johnston]. https://collections.library.yale.edu/catalog/16657578.