APA (7th ed.) Citation

Great Britain. Directorate of Overseas Surveys. (1968). Sierra Leone (Ed. 7-D.O.S.). The Directorate.

Chicago Style (17th ed.) Citation

Great Britain. Directorate of Overseas Surveys. Sierra Leone. Ed. 7-D.O.S. [Tolworth, England]: The Directorate, 1968.

MLA (9th ed.) Citation

Great Britain. Directorate of Overseas Surveys. Sierra Leone. Ed. 7-D.O.S. The Directorate, 1968.