MLA
Illustrated Post Card Co. (N.Y.). A horseless carriage : African American boy on a pig. unknown. Robert Langmuir African American Photograph Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/303qv9s4pn-cor.
APA, 6th edition
Illustrated Post Card Co. (N.Y.). (unknown)[A horseless carriage : African American boy on a pig]. Robert Langmuir African American Photograph Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/303qv9s4pn-cor.
Chicago
Illustrated Post Card Co. (N.Y.), A horseless carriage : African American boy on a pig, unknown, Robert Langmuir African American Photograph Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/303qv9s4pn-cor.