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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.128, Harvard University Press
Mahatma Gandhi (1965). “Glorious Thoughts of Gandhi: Being a Treasury of about Ten Thousand Valuable and Inspiring Thougths of Mahatma Gandhi, Classified Under Four Hundred Subjects”