On integral means of the derivatives of Blaschke products

抄録

Kutbi and Protas showed that if the zeros {a_k} of a given Blaschke product B satisfy Σ_k (1 - |a_k|)^α < ∞ for some α ∈ (0, 1), then the integral means of its derivative B⁽ⁿ⁾ satisfies certain estimate. In this paper, we extend their result.