MLA

Johnston, Alexander Keith, 1804-1871. Africa [cartographic material] / by A.K. Johnston F.R.G.S. ; engraved by W. & A.K. Johnston.. BRBL_00326. 1849?]. https://collections.library.yale.edu/catalog/15512994.

APA, 6th edition

Johnston, Alexander Keith, 1804-1871. (["BRBL_00326"])(1849?])[Africa [cartographic material] / by A.K. Johnston F.R.G.S. ; engraved by W. & A.K. Johnston.]. https://collections.library.yale.edu/catalog/15512994.