MLA

Anderson, Margaret C., 1886-1973. Kramer, Dorothy. Box 7, folder 107. 1973 September 28. https://collections.library.yale.edu/catalog/17099456.

APA, 6th edition

Anderson, Margaret C., 1886-1973. (["Box 7, folder 107"])(1973 September 28)[Kramer, Dorothy]. https://collections.library.yale.edu/catalog/17099456.