1. Whitham, G. (1974). Linear and Nonlinear Waves, John Wiley and Sons.
2. Graff, K. (1975). Wave Motion in Elastic Solids, Oxford University Press.
3. Jackson, J.D. (1992). Classical Electrodynamics, Wiley.
4. Morse, P.H., and Ingard, K.U. (1968). Theoretical Acoustics, McGraw-Hill.
5. Why do wave packets sometimes contract?;Cohen;J. Mod. Opt.,2003