Vibration of Continuous Systems by Singiresu S. Rao, Published by John Wiley & Sons, Inc., Hoboken, New Jersey.

Dynamics of Structures: Theory and Applications to Earthquake Engineering by Anil K. Chopra Published by Prentice-Hall International Series in Civil Engineering and Engineering M.

Vibrations and Waves in Continuous Mechanical Systems by P. Hagedorn and A. Das Gupta, Published by John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex PO19 8SQ, England.