Thorstein Veblen (2016). “THE THEORY OF THE LEISURE CLASS: An Economic Study of American Institutions and a Social Critique of Conspicuous Consumption: Development of Institutions That Shape Society and Influence the Livelihood of Citizens: Based on Sociological & Economical Theories of Charles Darwin, Karl Marx, Adam Smith and Herbert Spencer”, p.32, e-artnow
Ralph Waldo Emerson, Robert Ernest Spiller, Alfred Riggs Ferguson, Joseph Slater, Jean Ferguson Carr (1971). “The Collected Works of Ralph Waldo Emerson: Essays, second series”, p.124, Harvard University Press