MLA

Johnston, Alexander Keith, 1804-1871. United States and Texas [cartographic material] / by A.K. Johnston, Geographer to the Queen ; engraved by W. & A.K. Johnston.. [between 1840 and 1843]. https://collections.library.yale.edu/catalog/15536454.

APA, 6th edition

Johnston, Alexander Keith, 1804-1871. ([between 1840 and 1843])[United States and Texas [cartographic material] / by A.K. Johnston, Geographer to the Queen ; engraved by W. & A.K. Johnston.]. https://collections.library.yale.edu/catalog/15536454.