"Hermann Baumgarten" (in English). Encyclopædia Britannica Online. Retrieved 25 March 2010.
"Max Weber" (in English). Encyclopædia Britannica Online. Retrieved March 25, 2010.
cengage.com
college.cengage.com
McKay, John P.; Hill, Bennett D. (1999). "25". In Andrea Shaw (ed.). A History of Western Society. Buckler, John (6 ed.). Boston, MA: Houghton Mifflin Company. p. 832. ISBN0-395-90431-5. Archived from the original on Mar 25, 2010. Retrieved March 10, 2010.
McKay, John P.; Hill, Bennett D. (1999). "25". In Andrea Shaw (ed.). A History of Western Society. Buckler, John (6 ed.). Boston, MA: Houghton Mifflin Company. p. 832. ISBN0-395-90431-5. Archived from the original on Mar 25, 2010. Retrieved March 10, 2010.