Music/Songs (chorus)
MLA
Koch, Frederick R. (Frederick Robinson). Music/Songs (chorus). Box 345, folder 2039. n.d.. https://collections.library.yale.edu/catalog/2043659.
APA, 6th edition
Koch, Frederick R. (Frederick Robinson). (["Box 345, folder 2039"])(n.d.)[Music/Songs (chorus)]. https://collections.library.yale.edu/catalog/2043659.