Landau's Theorem

Theorem
Let $f: \C \to \C$ be a holomorphic function in the unit disk $\cmod z \le 1$.

Let $\cmod {\map {f'} 0} = 1$.

Then there exists:
 * a disk $D$ of radius $B$
 * an analytic function $\phi$ in $D$ such that $\map f {\map \phi z} = z$ for all $z$ in $D$

such that $L$ is an absolute constant where:
 * $L > B$

where $B$ is Bloch's constant.

Also see

 * Definition:Landau's Constant
 * Value of Landau's Constant


 * Bloch's Theorem
 * Definition:Bloch's Constant
 * Value of Bloch's Constant