MLA

Gombrowicz, Witold, 1904-1969. Sjöberg, Alf. Box 10, folder 374. 1966-68. https://collections.library.yale.edu/catalog/2007780.

APA, 6th edition

Gombrowicz, Witold, 1904-1969. (["Box 10, folder 374"])(1966-68)[Sjöberg, Alf]. https://collections.library.yale.edu/catalog/2007780.