MLA

Wolff, Helen, 1906-1994. Grass, Günter. Box 8, folder 347-354. 1959-69. https://collections.library.yale.edu/catalog/2021296.

APA, 6th edition

Wolff, Helen, 1906-1994. (["Box 8, folder 347-354"])(1959-69)[Grass, Günter]. https://collections.library.yale.edu/catalog/2021296.