MLA

Simpson, Randolph Linsly, 1927-1992. Studio unknown Full length portrait of Millie and Christine McCoy; conjoined twins seated on fringed chair. Cabinet photograph. Box 9, folder 194. circa 1870. https://collections.library.yale.edu/catalog/2002246.

APA, 6th edition

Simpson, Randolph Linsly, 1927-1992. (["Box 9, folder 194"])(circa 1870)[Studio unknown Full length portrait of Millie and Christine McCoy; conjoined twins seated on fringed chair. Cabinet photograph]. https://collections.library.yale.edu/catalog/2002246.