MLA

H. D. (Hilda Doolittle), 1886-1961. Ellis, Havelock. Box 52, folder 1329. n.d.. https://collections.library.yale.edu/catalog/2057146.

APA, 6th edition

H. D. (Hilda Doolittle), 1886-1961. (["Box 52, folder 1329"])(n.d.)[Ellis, Havelock]. https://collections.library.yale.edu/catalog/2057146.