MLA

of New York, American Geographical Society. Block Diagram Showing Terrain of the Balkan Peninsula [Cartographic Material]. The American Geographical Society, 1918. https://collections.library.yale.edu/catalog/15827159.

APA, 6th edition

of New York, A. G. S. (1918). Block diagram showing terrain of the Balkan Peninsula [cartographic material]. [Maps]. The American Geographical Society, https://collections.library.yale.edu/catalog/15827159.