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On some simple sufficient conditions for univalence

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126 (2001) MATHEMATICA BOHEMICA No. 1, 229–236<br />

ON SOME SIMPLE SUFFICIENT CONDITIONS FOR UNIVALENCE<br />

Nikola Tuneski, Skopje<br />

(Received June 8, 1999)<br />

Abstract. In this paper <strong>some</strong> <strong>simple</strong> <strong>conditions</strong> on f ′ (z) andf ′′ (z) whichleadto<strong>some</strong><br />

subclasses of univalent functions will be considered.<br />

Keywords: univalent, starlike, sharp result<br />

MSC 2000 : 30C45<br />

1. Introduction and preliminaries<br />

Let A denote the class of analytic functions f(z) in the unit disc U = {z : |z| < 1}<br />

and normalized so that f(0) = f ′ (0) − 1=0.<br />

A function f(z) ∈ A is said to be starlike of order α, i.e., to belong to S ∗ (α),<br />

0 αα<br />

f(z)<br />

<strong>for</strong> all z ∈ U. Then S ∗ = S ∗ (0) is the class of starlike functions in the unit disc<br />

U. Further, ˜S ∗ (α), 0

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