Cite

Berceuse for Little Helen, for violin [flute] & piano

MLA

Porter, Quincy, 1897-1966. Berceuse for Little Helen, for violin [flute] & piano. Box 43, folder 43. 1929. https://collections.library.yale.edu/catalog/32207245.

APA, 6th edition

Porter, Quincy, 1897-1966. (["Box 43, folder 43"])(1929)[Berceuse for Little Helen, for violin [flute] & piano]. https://collections.library.yale.edu/catalog/32207245.