MLA

Section, Great Britain. War Office. General Staff. Topographical. Province of Ssŭ-Ch'Uan / Compiled in the Topographic Section, General Staff. Reproduced and printed for the Topographical Section, General Staff, at the Ordnance Survey Office, 1908. https://collections.library.yale.edu/catalog/15827228.

APA, 6th edition

Section, G. B. W. O. G. S. T. (1908). Province of Ssŭ-ch'uan / compiled in the Topographic Section, General Staff. [Maps]. Reproduced and printed for the Topographical Section, General Staff, at the Ordnance Survey Office, https://collections.library.yale.edu/catalog/15827228.