MLA

Simpson, Randolph Linsly, 1927-1992. Lapel button, Two boys: one black, the other white lie in grass facing viewer; full color, split brass fastening, 1/3-4 diameter. Box 41, folder 1177. circa 1900. https://collections.library.yale.edu/catalog/9999055.

APA, 6th edition

Simpson, Randolph Linsly, 1927-1992. (["Box 41, folder 1177"])(circa 1900)[Lapel button, Two boys: one black, the other white lie in grass facing viewer; full color, split brass fastening, 1/3-4 diameter]. https://collections.library.yale.edu/catalog/9999055.