MLA

Simpson, Randolph Linsly, 1927-1992. Hughes & Co., Photographers, Troxel's Old Stand, S.W. Cor. 4th and Locust, St. Louis Full-length double portrait, Millie and Christine McCoy, conjoined twins, Carte de visite. Box 11, folder 462. circa 1860. https://collections.library.yale.edu/catalog/2004006.

APA, 6th edition

Simpson, Randolph Linsly, 1927-1992. (["Box 11, folder 462"])(circa 1860)[Hughes & Co., Photographers, Troxel's Old Stand, S.W. Cor. 4th and Locust, St. Louis Full-length double portrait, Millie and Christine McCoy, conjoined twins, Carte de visite]. https://collections.library.yale.edu/catalog/2004006.