MLA

Hansen, Bert, 1944-. "New York City. Sanitary Precaution against a smallpox epidemic. An Inspector of the Board of Health Vaccinating Tramps in a Station-House.". Box 2, folder 19. 1879 April 19. https://collections.library.yale.edu/catalog/32328872.

APA, 6th edition

Hansen, Bert, 1944-. (["Box 2, folder 19"])(1879 April 19)["New York City. Sanitary Precaution against a smallpox epidemic. An Inspector of the Board of Health Vaccinating Tramps in a Station-House."]. https://collections.library.yale.edu/catalog/32328872.