MLA

Steinberg, Saul, 1914-1999. Russia Winter 1956. Box 89, folder 1963. 1956. https://collections.library.yale.edu/catalog/2016703.

APA, 6th edition

Steinberg, Saul, 1914-1999. (["Box 89, folder 1963"])(1956)[Russia Winter 1956]. https://collections.library.yale.edu/catalog/2016703.