Variability regions of close-to-convex functions

Takao Kato, Toshiyuki Sugawa, Li-Mei Wang

M. Biernacki gave concrete forms of the variability regions of $z/f(z)$ and $z{f}^{\prime }(z)/f(z)$ of close-to-convex functions $f$ for a fixed $z$ with $|z|<1$ in 1936. The forms are, howe…