MLA

Marinetti, F. T., 1876-1944. 1906 Mar 5 2 p.; 1909 Ton poème sera écrit par Marie Kalff... 1 p. Written on verso of letter from Salon des Artistes Indépendants, (signed also by Pablo Picasso and Guillaume Apollinaire).. Box 12, folder 608. 1898-1970. https://collections.library.yale.edu/catalog/16687002.

APA, 6th edition

Marinetti, F. T., 1876-1944. (["Box 12, folder 608"])(1898-1970)[1906 Mar 5 2 p.; 1909 Ton poème sera écrit par Marie Kalff... 1 p. Written on verso of letter from Salon des Artistes Indépendants, (signed also by Pablo Picasso and Guillaume Apollinaire).]. https://collections.library.yale.edu/catalog/16687002.