Continuum Dynamics of Elastic Plates and Multilayered Solids Under Initial Stress M. Biot Indiana University Mathematics Journal 1963 text pdf 10.1512/iumj.1963.12.12055 10.1512/iumj.1963.12.12055 en Indiana Univ. Math. J. 12 (1963) 793 - 809 state-of-the-art mathematics http://iumj.org/access/