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。业内人士推荐体育直播作为进阶阅读
Виктория Кондратьева (Редактор отдела «Мир»)
Definition 3 A universal cover of a topological space \(X\) is a covering space \(\tilde{X}\) of \(X\) that is simply connected, meaning that it has no nontrivial loops. The universal cover is unique up to homeomorphism and serves as a “universal” object in the category of covering spaces of \(X\).