Compatibility Conditions of the Theory of Micromorphic Elastic Solids A. Eringen Indiana University Mathematics Journal 1970 text pdf 10.1512/iumj.1970.19.19044 10.1512/iumj.1970.19.19044 en Indiana Univ. Math. J. 19 (1970) 473 - 481 state-of-the-art mathematics http://iumj.org/access/