[ 1]. William James, Psychology, Briefer Course, p. 1.

[ 2]. Hugo Münsterberg, American Problems, p. 34.

[ 3]. Mary Whiton Calkins, A First Book in Psychology, p. 1.

[ 4]. James Sully, Teacher's Handbook of Psychology, p. 14.

[ 5]. James Sully, Teacher's Handbook of Psychology, p. 577.

[ 6]. H.L. Gantt, Work, Wages and Profits, p. 52.

[ 7]. F.W. Taylor, Shop Management, p. 25. (Harper & Bros.)

[ 8]. F.B. Gilbreth, Motion Study, p. 7.

[ 9]. L.B. Blan, A Special Study of the Incidence of Retardation, p. 89.