MLA

Simpson, Randolph Linsly, 1927-1992. Unknown Photographer Double portrait of young boy standing, young girl sitting, Carte de visite. Box 11, folder 491. 1860. https://collections.library.yale.edu/catalog/2003962.

APA, 6th edition

Simpson, Randolph Linsly, 1927-1992. (["Box 11, folder 491"])(1860)[Unknown Photographer Double portrait of young boy standing, young girl sitting, Carte de visite]. https://collections.library.yale.edu/catalog/2003962.