Jets with Two Fluids I: One Free Boundary Hans AltLuis CaffarelliAvner Friedman Indiana University Mathematics Journal 1984 text pdf 10.1512/iumj.1984.33.33011 10.1512/iumj.1984.33.33011 en Indiana Univ. Math. J. 33 (1984) 213 - 247 state-of-the-art mathematics http://iumj.org/access/