MLA

Marinetti, F. T., 1876-1944. Article in Bulgarian [or Russian] about folk songs. No source, [Mar 1933]. [6608-1]. box 83, slide 68. 1933. https://collections.library.yale.edu/catalog/10659094.

APA, 6th edition

Marinetti, F. T., 1876-1944. (["box 83, slide 68"])(1933)[Article in Bulgarian [or Russian] about folk songs. No source, [Mar 1933]. [6608-1]]. https://collections.library.yale.edu/catalog/10659094.