Spencer, H. (1876). The principles of sociology: Vol. I. Williams and Norgate.
Lua i Stíl Chicago (17ú heag.)Spencer, Herbert. The Principles of Sociology: Vol. I. London: Williams and Norgate, 1876.
Lua MLA (8ú heag.)Spencer, Herbert. The Principles of Sociology: Vol. I. Williams and Norgate, 1876.
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