MLA

West, Rebecca, 1892-1983. Kang, Younghill. Box 11, folder 451. n.d.. https://collections.library.yale.edu/catalog/17477075.

APA, 6th edition

West, Rebecca, 1892-1983. (["Box 11, folder 451"])(n.d.)[Kang, Younghill]. https://collections.library.yale.edu/catalog/17477075.