MLA

Dreier, Katherine S. (Katherine Sophie), 1877-1952. Gabo, Naum. Box 102, folder 2517-2519. 1923-51, n.d.. https://collections.library.yale.edu/catalog/2015206.

APA, 6th edition

Dreier, Katherine S. (Katherine Sophie), 1877-1952. (["Box 102, folder 2517-2519"])(1923-51, n.d.)[Gabo, Naum]. https://collections.library.yale.edu/catalog/2015206.