MLA

Pratt, Richard Henry, 1840-1924. Fort Marion (stereograms), 18 items. Box 23a, folder 744. n.d.. https://collections.library.yale.edu/catalog/2018526.

APA, 6th edition

Pratt, Richard Henry, 1840-1924. (["Box 23a, folder 744"])(n.d.)[Fort Marion (stereograms), 18 items]. https://collections.library.yale.edu/catalog/2018526.