Stratton, Experimental Psychology and Culture, p. 11.

Mary Whiton Calkins, A First Book in Psychology, p. 65.

C.G. Barth, A.S.M.E., Vol. 25, Paper 1010, p. 46.

Charles Babbage, On the Economy of Machinery and Manufactures, Secs. 224-225. Adam Smith, Wealth of Nations, Book 1, chap. 1, p. 4.

F.W. Taylor, paper 1119, A.S.M.E., para. 51; para. 98-100.

F.A. Parkhurst, Applied Methods of Scientific Management, Industrial Engineering, Oct. 1911, p. 251.

H.L. Gantt, paper 928, A.S.M.E., para. 15.

Gillette and Dana, Cost Keeping and Management Engineering, p. 65.