MLA

Allen, Nathaniel T. (Nathaniel Topliff), 1823-1903. Mineral specimens catalog. Box 2, folder 18. undated. https://collections.library.yale.edu/catalog/30997389.

APA, 6th edition

Allen, Nathaniel T. (Nathaniel Topliff), 1823-1903. (["Box 2, folder 18"])(undated)[Mineral specimens catalog]. https://collections.library.yale.edu/catalog/30997389.