Uniqueness of planar tangent maps in the modified Ericksen model Onur Alper Indiana University Mathematics Journal 2019 text pdf 10.1512/iumj.2019.68.7733 10.1512/iumj.2019.68.7733 en Indiana Univ. Math. J. 68 (2019) 1255 - 1275 state-of-the-art mathematics http://iumj.org/access/