CONVOLUTION OF FUNCTIONS WITH FREE NORMALIZATION
Krzysztof Piejko, Jan Stankiewicz · Demonstratio Mathematica · 2001
Let A denotes the unit disc and let Ti. be the class of functions regular in A. For two functions f(z) = anz n , g(z) -bnz n of the class H we define the convolution as follows (/ * g)(z) := anbnz n .In this paper we determine the domain D3 such that (f + g) (A) C D3 for every two functions f,g € H said such that /(A) C D\, g{A) C D2, where D\ and £>2 are the given circular (disc, halfplane) or angularly domains.1991