MLA

Du Bois, W. E. B. (William Edward Burghardt), 1868-1963. Poem, typescript, corrected. Box 3, folder 61. n.d.. https://collections.library.yale.edu/catalog/16732028.

APA, 6th edition

Du Bois, W. E. B. (William Edward Burghardt), 1868-1963. (["Box 3, folder 61"])(n.d.)[Poem, typescript, corrected]. https://collections.library.yale.edu/catalog/16732028.