Cite

Snapshots from the train. The Rocky Mountains. No. 21.

MLA

Ingersoll, Ernest, 1852-1946, Jackson, William Henry, 1843-1942. Snapshots from the train. The Rocky Mountains. No. 21.. https://collections.library.yale.edu/catalog/2018681.

APA, 6th edition

Ingersoll, Ernest, 1852-1946, & Jackson, William Henry, 1843-1942. [Snapshots from the train. The Rocky Mountains. No. 21.]. https://collections.library.yale.edu/catalog/2018681.