MLA

Marinetti, F. T., 1876-1944. Herwarth Walden. “Die Freiheit in der Fachkritik.” Der Sturm, [1934]. [9063-1]. box 114, slide 43. 1934. https://collections.library.yale.edu/catalog/10663681.

APA, 6th edition

Marinetti, F. T., 1876-1944. (["box 114, slide 43"])(1934)[Herwarth Walden. “Die Freiheit in der Fachkritik.” Der Sturm, [1934]. [9063-1]]. https://collections.library.yale.edu/catalog/10663681.