Plastic Flow and Fracture in Solids T. Thomas Indiana University Mathematics Journal 1958 text pdf 10.1512/iumj.1958.7.57021 10.1512/iumj.1958.7.57021 en Indiana Univ. Math. J. 7 (1958) 291 - 322 state-of-the-art mathematics http://iumj.org/access/