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.48, e-artnow
Aristotle, (2016). “Aristotle's Politics: Writings from the Complete Works: Politics, Economics, Constitution of Athens”, p.214, Princeton University Press