MLA

Marinetti, F. T., 1876-1944. Reproduction of letter, dated "Maj 1857," from Cypryan Norwid to Szanowny Wladyslawie. [Zdroj?]. In Polish. [1496-1]. box 19, slide 76. no date. https://collections.library.yale.edu/catalog/10650691.

APA, 6th edition

Marinetti, F. T., 1876-1944. (["box 19, slide 76"])(no date)[Reproduction of letter, dated "Maj 1857," from Cypryan Norwid to Szanowny Wladyslawie. [Zdroj?]. In Polish. [1496-1]]. https://collections.library.yale.edu/catalog/10650691.