MLA

Marinetti, F. T., 1876-1944. Anonymous. “Une reponse a la lettre de Maurice Bedel à Marinetti.” No source, [1929]. [5785-1]. box 73, slide 45. 1929. https://collections.library.yale.edu/catalog/10657796.

APA, 6th edition

Marinetti, F. T., 1876-1944. (["box 73, slide 45"])(1929)[Anonymous. “Une reponse a la lettre de Maurice Bedel à Marinetti.” No source, [1929]. [5785-1]]. https://collections.library.yale.edu/catalog/10657796.