Key to Gray & Gifford's view of San Francisco, 1868
MLA
Gray, W. Vallance, et al. Key to Gray & Gifford's View of San Francisco, 1868. 1868. https://collections.library.yale.edu/catalog/2016495.
APA, 6th edition
Gray, W. V., C. B. Gifford, S. F., & C. (1868). Key to Gray & Gifford's view of San Francisco, 1868 [Lithographs, Planographic prints]. https://collections.library.yale.edu/catalog/2016495.