2003年刘提出的图的联树（1979的文章体现了这种思想）为嵌入亏格分布的研究提供了理论基础。
Liu created joint trees, initiated in his early paper in 1979, of a graph in 2003 which provided a foundation on studying embedding genus distribution.
本文研究属第一个方面，即研究图的嵌入的最大亏格问题。
There are two fields in topological graph theory: one is the study of the properties of graph embedding.
这就是图的嵌入亏格分布问题。
This is the problem of embedding genus distribution for a graph.
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