APA (7th ed.) Citation

National Gallery (London). (1921). National Gallery Trafalgar Square. Illustrated guide. H.M.S.O.

Chicago Style (17th ed.) Citation

National Gallery (London). National Gallery Trafalgar Square. Illustrated Guide. London: H.M.S.O, 1921.

MLA (9th ed.) Citation

National Gallery (London). National Gallery Trafalgar Square. Illustrated Guide. H.M.S.O, 1921.

Warning: These citations may not always be 100% accurate.