Existence and Uniqueness of Solutions to a Nonlinear Boundary Value Problem Paul Waltman Indiana University Mathematics Journal 1969 text pdf 10.1512/iumj.1969.18.18045 10.1512/iumj.1969.18.18045 en Indiana Univ. Math. J. 18 (1969) 585 - 586 state-of-the-art mathematics http://iumj.org/access/