Cite

Two Pieces for Organ, Opus 6 (never published)

MLA

Baumgartner, H. Leroy (Hope Leroy), 1891-1969. Two Pieces for Organ, Opus 6 (never published). Box 1, folder 6. undated. https://collections.library.yale.edu/catalog/32208325.

APA, 6th edition

Baumgartner, H. Leroy (Hope Leroy), 1891-1969. (["Box 1, folder 6"])(undated)[Two Pieces for Organ, Opus 6 (never published)]. https://collections.library.yale.edu/catalog/32208325.