MLA

Cullen, Countee, 1903-1946. Holograph notebook with other poems. Box 2, folder 26. 1928-29. https://collections.library.yale.edu/catalog/2066730.

APA, 6th edition

Cullen, Countee, 1903-1946. (["Box 2, folder 26"])(1928-29)[Holograph notebook with other poems]. https://collections.library.yale.edu/catalog/2066730.