MLA

Pratt, Richard Henry, 1840-1924. Lantern slides of selected visual materials in the Pratt Papers, assorted subjects, 38 items. Box 23b, folder 751a. n.d.. https://collections.library.yale.edu/catalog/2041183.

APA, 6th edition

Pratt, Richard Henry, 1840-1924. (["Box 23b, folder 751a"])(n.d.)[Lantern slides of selected visual materials in the Pratt Papers, assorted subjects, 38 items]. https://collections.library.yale.edu/catalog/2041183.