MLA

Speck, William A. (William Alfred), 1864-1928. [Mignon's Lied: Kennst du das Land? Gedicht von Goethe. Music von Franz Liszt]. Box 1, folder 7. n.d.. https://collections.library.yale.edu/catalog/11243486.

APA, 6th edition

Speck, William A. (William Alfred), 1864-1928. (["Box 1, folder 7"])(n.d.)[[Mignon's Lied: Kennst du das Land? Gedicht von Goethe. Music von Franz Liszt]]. https://collections.library.yale.edu/catalog/11243486.