MLA

Douglas, Norman, 1868-1952. "Arcades Ambo," holograph. Box 43, folder 14. undated. https://collections.library.yale.edu/catalog/31001528.

APA, 6th edition

Douglas, Norman, 1868-1952. (["Box 43, folder 14"])(undated)["Arcades Ambo," holograph]. https://collections.library.yale.edu/catalog/31001528.