Ratio Limit Theorems for Hitting Times and Hitting Places Samuel Oman Indiana University Mathematics Journal 1978 text pdf 10.1512/iumj.1978.27.27043 10.1512/iumj.1978.27.27043 en Indiana Univ. Math. J. 27 (1978) 657 - 670 state-of-the-art mathematics http://iumj.org/access/