Ralph Waldo Emerson, Robert Ernest Spiller, Alfred Riggs Ferguson, Joseph Slater, Jean Ferguson Carr (1971). “The Collected Works of Ralph Waldo Emerson: Nature, addresses, and lectures”, p.64, Harvard University Press
Ralph Waldo Emerson, Alfred R. Ferguson (1965). “Journals and Miscellaneous Notebooks of Ralph Waldo Emerson, Volume V: 1835-1838”, p.233, Harvard University Press
Ralph Waldo Emerson, Robert Ernest Spiller, Alfred Riggs Ferguson, Joseph Slater, Jean Ferguson Carr (1971). “The Collected Works of Ralph Waldo Emerson: Nature, addresses, and lectures”, p.69, Harvard University Press