MLA

Low, David, 1891-1963. "The Midnight Watch: Wall Sheet of Britain's Fire Guard and Civil Defense Workers". Box 24, folder 1043a. ca. 1939. https://collections.library.yale.edu/catalog/10170911.

APA, 6th edition

Low, David, 1891-1963. (["Box 24, folder 1043a"])(ca. 1939)["The Midnight Watch: Wall Sheet of Britain's Fire Guard and Civil Defense Workers"]. https://collections.library.yale.edu/catalog/10170911.