MLA

Dreier, Katherine S. (Katherine Sophie), 1877-1952. Peri, Laszlo. Box 110, folder 2666. 1949, n.d.. https://collections.library.yale.edu/catalog/2015227.

APA, 6th edition

Dreier, Katherine S. (Katherine Sophie), 1877-1952. (["Box 110, folder 2666"])(1949, n.d.)[Peri, Laszlo]. https://collections.library.yale.edu/catalog/2015227.