Uniqueness and Regularity of Proper Harmonic Maps II Ping LiLuen-Fai Tam Indiana University Mathematics Journal 1993 text pdf 10.1512/iumj.1993.42.42027 10.1512/iumj.1993.42.42027 en Indiana Univ. Math. J. 42 (1993) 591 - 635 state-of-the-art mathematics http://iumj.org/access/