MLA

H. D. (Hilda Doolittle), 1886-1961. Herring, Robert. Box 11, folder 365-70. 1949-61, n.d.. https://collections.library.yale.edu/catalog/17064195.

APA, 6th edition

H. D. (Hilda Doolittle), 1886-1961. (["Box 11, folder 365-70"])(1949-61, n.d.)[Herring, Robert]. https://collections.library.yale.edu/catalog/17064195.