APA (7th ed.) Citation

Imperial War Museum (Great Britain), Slocombe, R., & Steel, N. (2014). Posters of the First World War. Imperial War Museum.

Chicago Style (17th ed.) Citation

Imperial War Museum (Great Britain), Richard Slocombe, and Nigel Steel. Posters of the First World War. London: Imperial War Museum, 2014.

MLA (9th ed.) Citation

Imperial War Museum (Great Britain), et al. Posters of the First World War. Imperial War Museum, 2014.