Cite

Key to Gray & Gifford's view of San Francisco, 1868

MLA

Key to Gray & Gifford's View of San Francisco, 1868. W. Vallance Gray & C.B. Gifford?, 0AD. https://collections.library.yale.edu/catalog/2016495.

APA, 6th edition

Key to Gray & Gifford's view of San Francisco, 1868. (0 C.E.). [Aerial views, Indexes, Lithographs]. W. Vallance Gray & C.B. Gifford? https://collections.library.yale.edu/catalog/2016495.