Kurt Lewin (1890–1947) German-American psychologist
Kurt Lewin (1927, p. 305) as cited in: K. Mulligan & B. Smith (1988) " Mach and Ehrenfels: Foundations of Gestalt Theory http://ontology.buffalo.edu/smith/articles/mach/mach.pdf". p. 149. <br class="br">1920s