MLA

Cowardly Assassination. Lecompton Union Extra! 1857. https://collections.library.yale.edu/catalog/10563285.

APA, 6th edition

Cowardly assassination. Lecompton union extra! (1857). [Annotations, Broadsides, clippings (information artifacts) (AAT)]. https://collections.library.yale.edu/catalog/10563285.