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| In this paper, we obtain some criteria for normal functions that share sets with their derivatives. The main result is:Let $S_1={a_1, a_2}$ and $ S_2={b_1, b_2}$ be two sets in $Bbb C$ such that $a_1a_2
eq 0$ and $b_1/b_2
otin Bbb{Z}^-cup1/Bbb{Z}^-$. Let $f$ be a meromorphic function in the unit disc $Delta$, and suppose that there exists a positive number $M$ such that $|f'(z)|leq M$ whenever $f(z)=0$. If $fin S_1 Leftrightarrow f'in S_2$ in $Delta$, then $f$ is normal. Here $Bbb{Z}^-$ denotes the set of all negative integers, and $1/Bbb{Z}^-$ stands for the set ${1/k; kin Bbb{Z}^-}$. |
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| Keywords:meromorphic functions, normal functions, shared sets |
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