The National Gallery companion guide (London).

MLA

Langmuir, Erika, and Neil MacGregor. The National Gallery Companion Guide (london). London: National Gallery Publications, 1994.

APA

Langmuir, E., & MacGregor, N. (1994). The National Gallery companion guide (London). London: National Gallery Publications.

Chicago

Langmuir, Erika, and Neil MacGregor. The National Gallery Companion Guide (london). London: National Gallery Publications, 1994.