MLA

Gabo, Naum, 1890-1977. Cornford, Christopher. Box 6. 1939-1980. https://collections.library.yale.edu/catalog/2055170.

APA, 6th edition

Gabo, Naum, 1890-1977. (["Box 6"])(1939-1980)[Cornford, Christopher]. https://collections.library.yale.edu/catalog/2055170.