MLA

Marinetti, F. T., 1876-1944. 1926 May 15 Telegram; 1926 May 19 2 p. Telegram; 1926 May 21 Telegram; 1926 May 23 2 p. Telegram; the only telegram stamped by the sender.; 1926 May 28 Telegram; 1926 May 31 Telegram; 1926 Jun 7 Telegram. Box 7, folder 76. 1898-1970. https://collections.library.yale.edu/catalog/16686998.

APA, 6th edition

Marinetti, F. T., 1876-1944. (["Box 7, folder 76"])(1898-1970)[1926 May 15 Telegram; 1926 May 19 2 p. Telegram; 1926 May 21 Telegram; 1926 May 23 2 p. Telegram; the only telegram stamped by the sender.; 1926 May 28 Telegram; 1926 May 31 Telegram; 1926 Jun 7 Telegram]. https://collections.library.yale.edu/catalog/16686998.