MLA

Anderson, Margaret C., 1886-1973. Poems, drafts. Box 17, folder 321. undated. https://collections.library.yale.edu/catalog/32268679.

APA, 6th edition

Anderson, Margaret C., 1886-1973. (["Box 17, folder 321"])(undated)[Poems, drafts]. https://collections.library.yale.edu/catalog/32268679.