MLA

Dexter, Franklin Bowditch, 1842-1920, Yale University. Library, author. Index to slavery pamphlets, Library of Americana, etc.. [between 1867?-1907?]. https://collections.library.yale.edu/catalog/11530123.

APA, 6th edition

Dexter, Franklin Bowditch, 1842-1920, & Yale University. Library, author. ([between 1867?-1907?])[Index to slavery pamphlets, Library of Americana, etc.]. https://collections.library.yale.edu/catalog/11530123.