A Converse of Taylor's Theorem Felix AlbrechtHarold Diamond Indiana University Mathematics Journal 1972 text pdf 10.1512/iumj.1972.21.21025 10.1512/iumj.1972.21.21025 en Indiana Univ. Math. J. 21 (1972) 347 - 350 state-of-the-art mathematics http://iumj.org/access/