John Greenleaf Whittier (2012). “Songs of Labor and Reform From Volume III., the Works of Whittier: Anti-Slavery Poems and Songs of Labor and Reform”, p.32, tredition
Henry David Thoreau (2017). “HENRY DAVID THOREAU – The Man, The Philosopher & The Trailblazer (Illustrated): Biographies, Memoirs, Autobiographical Books & Personal Letters (Including Walden, A Week on the Concord and Merrimack Rivers, The Maine Woods, Cape Cod, A Yankee in Canada…)”, p.37, e-artnow