MLA

Dreier, Katherine S. (Katherine Sophie), 1877-1952. Moholy-Nagy, Lucia. Sixth International Congress for Drawing, Art Education, and Applied Arts (Prague). Box 74, folder 1939. 1928 Aug. https://collections.library.yale.edu/catalog/33111588.

APA, 6th edition

Dreier, Katherine S. (Katherine Sophie), 1877-1952. (["Box 74, folder 1939"])(1928 Aug)[Moholy-Nagy, Lucia. Sixth International Congress for Drawing, Art Education, and Applied Arts (Prague)]. https://collections.library.yale.edu/catalog/33111588.