Janowski starlikeness for a class of analytic functions

A normalized analytic function f defined on the open unit disk is a Janowski starlike function if z f ′ ( z ) / f ( z ) is subordinated to ( 1 + A z ) / ( 1 + B z ) , where A and B are complex numbers satisfying the conditions | B | ≤ 1 and A ≠ B . In this paper, a new class of analytic functions defined by means of subordination is introduced. Sufficient conditions are obtained for functions in this class to be Janowski starlike. The results obtained extend earlier known works.