Nelson A. Miles (1992). “Personal Recollections and Observations of General Nelson A. Miles, Embracing a Brief View of the Civil War, Or, From New England to the Golden Gate and the Story of His Indian Campaigns with Comments on the Exploration, Development, and Progress of Our Great Western Empire”, p.339, U of Nebraska Press
John Stuart Mill (1856). “A System of Logic, Ratiocinative and Inductive, Being a Connected View of the Principles, and the Methods of Scientific Investigation”, p.16