Cite

["Understand that you can have in your writing..."], holograph, corrected

MLA

Whitman, Walt, 1819-1892. ["Understand that you can have in your writing..."], holograph, corrected. Box 1, folder 42. n.d.. https://collections.library.yale.edu/catalog/2053676.

APA, 6th edition

Whitman, Walt, 1819-1892. (["Box 1, folder 42"])(n.d.)[["Understand that you can have in your writing..."], holograph, corrected]. https://collections.library.yale.edu/catalog/2053676.