  In this paper we will show that the assumption on the negative Schwarzian
derivative is redundant in the case of C^3 unimodal maps with a nonflat
critical point. The following theorem will be proved: For any C^3 unimodal map
of an interval with a nonflat critical point there exists an interval around
the critical value such that the first entry map to this interval has negative
Schwarzian derivative. Another theorem proved in the paper provides useful
cross-ratio estimates. Thus, all theorems proved only for unimodal maps with
negative Schwarzian derivative can be easily generalized.
