On harmonic univalent functions defined by a generalized Ruscheweyh derivatives operator

(Lobachevskii Journal of Mathematics, Volume XXII)

Let S_H denote the class of functions f=h+g which are harmonic univalent and sense preserving in the unit disk U. Al-Shaqsi and Darus introduced a generalized Ruscheweyh derivatives operator denoted by Dⁿ_λ where Dⁿ_λ f(z)= z+ Σ_{k = 2}^∞ [1+λ(k-1)]C(n,k)a_kz^k. The authors, using this operators, introduce the class Hⁿ_λ of functions which are harmonic in U . Coefficient bounds, distortion bounds and extreme points are obtained.