1. 3. Clarence Zener , Elasticity and Anelasticity of Metals pp.56 -57 . University of Chicago Press, Chicago. 1948 .
2. Apparatus for Measurement of Viscoelastic Properties of Glass
3. 5. H. W. Reddick, and F. H. Miller , Advanced Mathematics for Engineers , pp.379 -80 . John Wiley & Sons, Inc., New York, 1938 .