Libretto in English, by Spender (autograph manuscript and typescript)
MLA
Nabokov, Nicolas, 1903-1978. Libretto in English, by Spender (autograph manuscript and typescript). Box 5, folder 79. undated. https://collections.library.yale.edu/catalog/30996449.
APA, 6th edition
Nabokov, Nicolas, 1903-1978. (["Box 5, folder 79"])(undated)[Libretto in English, by Spender (autograph manuscript and typescript)]. https://collections.library.yale.edu/catalog/30996449.