Some Properties of f''/f' and the Poincare Metric B. Osgood Indiana University Mathematics Journal 1982 text pdf 10.1512/iumj.1982.31.31037 10.1512/iumj.1982.31.31037 en Indiana Univ. Math. J. 31 (1982) 449 - 461 state-of-the-art mathematics http://iumj.org/access/