Proceedings of the American Mathematical Society

Author(s): Walter Bergweiler
Journal: Proc. Amer. Math. Soc. 129 (2001), 121-129.
MSC (1991): Primary 30D45, 30D30
Posted: June 21, 2000
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We show that a family $\mathcal{F}$ of functions meromorphic in some domain is normal, if for all $f\in\mathcal{F}$ the derivative

omits the value

and if the values that

can take at the zeros of

satisfy certain restrictions. As an application we obtain a new proof of a theorem of Langley which classifies the functions

meromorphic in the plane such that

and

have no zeros.

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