Cite

ALS to her son, Horatio

MLA

Harkness, Mary Emma Stillman, 1874-1950. ALS to her son, Horatio. Box 3, folder 14. n.d.. https://collections.library.yale.edu/catalog/33449134.

APA, 6th edition

Harkness, Mary Emma Stillman, 1874-1950. (["Box 3, folder 14"])(n.d.)[ALS to her son, Horatio]. https://collections.library.yale.edu/catalog/33449134.