MLA

Stenzel, Franz (1906-1998). [House, with a flower on verso.] Pencil drawing. Flower is watercolor, 17.5 x 25.4 cm.. Box 8, folder 150. n.d.. https://collections.library.yale.edu/catalog/2003266.

APA, 6th edition

Stenzel, Franz (1906-1998). (["Box 8, folder 150"])(n.d.)[[House, with a flower on verso.] Pencil drawing. Flower is watercolor, 17.5 x 25.4 cm.]. https://collections.library.yale.edu/catalog/2003266.