Janowski starlikeness for a class of analytic functions

A normalized analytic function ff defined on the open unit disk is a Janowski starlike function if zf′(z)/f(z)zf′(z)/f(z) is subordinated to (1+Az)/(1+Bz)(1+Az)/(1+Bz), where AA and BB are complex numbers satisfying the conditions |B|≤1|B|≤1 and A≠BA≠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.