ON SAKAGUCHI CLASSES OF SCHLICHT FUNCTIONS

Let f(z)=z+■be analytic in theopen disc U: |z| <1 and D^0f=f, D^1f(z)=zf’(z), D^2f = D(Df)=z(zf’(z))’, …, D^nf=D(D^n-~1f), (n≥1). If for a non-negative integer n and a positive integer k, there exists a constant α such that (ε~κ=1)