We describe a finite presentation of $ \mathcal{T}_{g,r} $ for $g \geq 3$. %or $(g,r)=(2,0)$. Here $\mathcal{T}_{g,r} $ is the universal central extensionof the mapping class group of the surface of genus $g$ with $r$-boundaries. Wealso investigate the case $g=2$,
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机译:我们描述了$ g \ geq 3 $的$ \ mathcal {T} _ {g,r} $的有限表示形式。 %或$(g,r)=(2,0)$。 $ \ mathcal {T} _ {g,r} $是$ g $属曲面的映射类组的通用中心扩展,具有$ r $边界。我们还要调查$ g = 2 $的情况,
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