MLA

Simpson, Randolph Linsly, 1927-1992. Franz Huld, Publisher, New York "Cake Walk (Negro Dance) No. 2" Four performers in costume, mid dance. Postcard in color. Box 25. 1898. https://collections.library.yale.edu/catalog/2005987.

APA, 6th edition

Simpson, Randolph Linsly, 1927-1992. (["Box 25"])(1898)[Franz Huld, Publisher, New York "Cake Walk (Negro Dance) No. 2" Four performers in costume, mid dance. Postcard in color]. https://collections.library.yale.edu/catalog/2005987.