APA (7th ed.) Citation

United States. Army. Signal Corps. (1874). [Indexing of letters at Signal Office observation stations]. [publisher not identified].

Chicago Style (17th ed.) Citation

United States. Army. Signal Corps. [Indexing of Letters at Signal Office Observation Stations]. [Washington]: [publisher not identified], 1874.

MLA (9th ed.) Citation

United States. Army. Signal Corps. [Indexing of Letters at Signal Office Observation Stations]. [publisher not identified], 1874.

Warning: These citations may not always be 100% accurate.