Spencer, H. (1899). The principles of psychology (4a ed.). Williams and Norgate.
Cita Chicago Style (17a ed.)Spencer, Herbert. The Principles of Psychology. 4a ed. London: Williams and Norgate, 1899.
Cita MLA (9a ed.)Spencer, Herbert. The Principles of Psychology. 4a ed. Williams and Norgate, 1899.
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