Variation Quotes
"Basic Statistical Tools for Improving Quality". Book by Chang W. Kang, Paul H. Kvam, p. 19, 2012.
Postulate 3. Assignable causes of variation may be found and eliminated.
"Economic Control of Quality of Manufactured Product". Book by Walter A. Shewhart, p. 8, 1931.
David Ricardo (1821). “On the Principles of Political Economy, and Taxation”, p.47
Gichin Funakoshi (1994). “Karate-dō Nyūmon: The Master Introductory Text”, p.44, Kodansha International
"Voices of German Expressionism" edited by Victor H. Miesel, Tate publishing, London, (p. 18), 2003.
Charles Darwin (2015). “Delphi Complete Works of Charles Darwin (Illustrated)”, p.3702, Delphi Classics