MLA

H. D. (Hilda Doolittle), 1886-1961. Macpherson, Kenneth. Box 12, folder 415-28. 1927-61, n.d.. https://collections.library.yale.edu/catalog/10187247.

APA, 6th edition

H. D. (Hilda Doolittle), 1886-1961. (["Box 12, folder 415-28"])(1927-61, n.d.)[Macpherson, Kenneth]. https://collections.library.yale.edu/catalog/10187247.