Spencer, Herbert - The Principles of Psychology. Longman, Brown, Green and Longmans, Londres, 1855 (E-Book in PDF format published by Liberty Fund, Inc., a private, non-profit, educational foundation. From The Online Library of Liberty web site)
Spencer, Herbert - The Principles of Psychology. Longman, Brown, Green and Longmans, Londres, 1855 (E-Book in PDF format published by Liberty Fund, Inc., a private, non-profit, educational foundation. From The Online Library of Liberty web site)