1. 6) Ralph M.Barnes,M.E.Mundel,John M.MacKenzie: Studies of One- and Two-Handed Work,University of Iowa Studies in Engineering,(1940)5.
2. 7) Ralph M Barnes.,M.E.Mundel, A Study of Simultaneous Symmerical Hand Motion,University of Iowa Studies in Engineering,(1939)3.
3. 8) R.M.Barnes: Motion and Time Study Design and Measurement of Work, John Wiley Sons,(1980)173.
4. 9) R.M.Barnes: Motion and Time Study Design and Measurement of Work,John Wiley Sons,(1980)202.
5. 11) Ralph M.Barnes, James S.Perkins, J.M.Juran : A Study of the Effect of Practice on the Elements of a Factory Operation,University of Iowa Studies in Engineering,(1940)73.