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(8) Tarde, Gabriel. "L'hérédité des professions," Revue internationale de sociologie, VIII (1900), 50-59. [Discussion of the subject was continued under the title "L'hérédité et la continuité des professions," pp. 117-24, 196-207.]
(9) Knapp, Georg F. Die Bauernbefreiung und der Ursprung der Landarbeiter in den älteren Theilen Preussens. Leipzig, 1887.
(10) Zimmern, Alfred E. The Greek Commonwealth. Politics and economics in fifth-century Athens. Pp. 255-73, 323-47, 378-94. 2d rev. ed. Oxford, 1915.
(11) Mallock, W. H. Aristocracy and Evolution. A study of the rights, the origin, and the social functions of the wealthier classes. New York, 1898.
(12) Veblen, Thorstein. The Theory of the Leisure Class. An economic study in the evolution of institutions. New York, 1899.
(13) D'Aeth, F. G. "Present Tendencies of Class Differentiation," Sociological Review, III (1910), 267-76.