MLA

Dreier, Katherine S. (Katherine Sophie), 1877-1952. At easel, in smock, holding palette, proof; In smock, holding palette; Studio portrait, wearing coat, with muff. Box 70, folder 1792. circa 1911-1912, undated. https://collections.library.yale.edu/catalog/17266186.

APA, 6th edition

Dreier, Katherine S. (Katherine Sophie), 1877-1952. (["Box 70, folder 1792"])(circa 1911-1912, undated)[At easel, in smock, holding palette, proof; In smock, holding palette; Studio portrait, wearing coat, with muff]. https://collections.library.yale.edu/catalog/17266186.