MLA

Hobson, J. B. Geological Map of the Iowa Hill Mining District, Placer County / by J.B. Hobson, E.M., Assistant in the Field. California State Mining Bureau, 0AD. https://collections.library.yale.edu/catalog/15821453.

APA, 6th edition

Hobson, J. B. (0 C.E.). Geological map of the Iowa Hill Mining District, Placer County / by J.B. Hobson, E.M., assistant in the field. [Maps]. California State Mining Bureau, https://collections.library.yale.edu/catalog/15821453.