Thomas Jefferson (2011). “Jefferson on Freedom: Wisdom, Advice, and Hints on Freedom, Democracy, and the American Way”, p.39, Skyhorse Publishing, Inc.
Lord Philip Dormer Stanhope Chesterfield, Philip Dormer Stanhope Earl of Chesterfield (1855). “The Works of Lord Chesterfield: Including His Letters to His Son, Etc : to which is Prefixed, an Original Life of the Author”, p.629
Calvin Coolidge (1972). “Calvin Coolidge says: dispatches written by former-president Coolidge and syndicated to newspapers in 1930-1931 : gathered for issuance in book form on the one-hundredth anniversary of Mr. Coolidge's birth, 4 July 1972”