MLA

Stevenson, Robert Louis, 1850-1894. "To Princess Kaiulani," poem, holograph. Box 10, folder 173. 1889 April 24. https://collections.library.yale.edu/catalog/16598951.

APA, 6th edition

Stevenson, Robert Louis, 1850-1894. (["Box 10, folder 173"])(1889 April 24)["To Princess Kaiulani," poem, holograph]. https://collections.library.yale.edu/catalog/16598951.