Existence of Solutions to the Nonhomogeneous Steady Navier-Stokes Equations Charles Amick Indiana University Mathematics Journal 1984 text pdf 10.1512/iumj.1984.33.33043 10.1512/iumj.1984.33.33043 en Indiana Univ. Math. J. 33 (1984) 817 - 830 state-of-the-art mathematics http://iumj.org/access/