MLA

Simpson, Randolph Linsly, 1927-1992. Miniature triple portrait of three nuns. Tintype, smaller than sixteenth plate. Box 7, folder 145. undated. https://collections.library.yale.edu/catalog/2002210.

APA, 6th edition

Simpson, Randolph Linsly, 1927-1992. (["Box 7, folder 145"])(undated)[Miniature triple portrait of three nuns. Tintype, smaller than sixteenth plate]. https://collections.library.yale.edu/catalog/2002210.