MLA

Carlyle, Thomas, 1795-1881. Carlyle, Thomas, manuscript relating to Oliver Cromwell's Letters and Speeches," holograph. Box 15. undated. https://collections.library.yale.edu/catalog/2007491.

APA, 6th edition

Carlyle, Thomas, 1795-1881. (["Box 15"])(undated)[Carlyle, Thomas, manuscript relating to Oliver Cromwell's Letters and Speeches," holograph]. https://collections.library.yale.edu/catalog/2007491.