MLA

Campbell, Gladys, 1892-1992. Slavick, William. Box 2, folder 49. 1981. https://collections.library.yale.edu/catalog/17209859.

APA, 6th edition

Campbell, Gladys, 1892-1992. (["Box 2, folder 49"])(1981)[Slavick, William]. https://collections.library.yale.edu/catalog/17209859.