MLA

Bahlmann, Anna Catherine, 1849-1916. Postcards albums. Box 7, folder 210-260. undated. https://collections.library.yale.edu/catalog/2111658.

APA, 6th edition

Bahlmann, Anna Catherine, 1849-1916. (["Box 7, folder 210-260"])(undated)[Postcards albums]. https://collections.library.yale.edu/catalog/2111658.