1. 1S. Timoshenko, and J. M. Lessels , Applied Elasticity , 1st ed. , p.52 . Westinghouse Technical Night School Press, East Pittsburgh, Pa., 1925 .
2. 2M. O. Withey, and James Aston , Johnson's Materials of Construction , 8th ed. , p.4 . John Wiley and Sons, Inc., New York, N. Y., 1939 .
3. 3International Critical Tables of Numerical Data, Physics, Chemistry and Technology , 1st ed. , Vol. II , p.93 . McGraw-Hill Book Co., Inc., New York, N. Y., 1927 .
4. 4Standard Methods of Tension Testing of Metallic Materials (E8 -42 ). 1944 Book of A.S.T.M. Standards, Part I, p.8 .