This is to acknowledge that the main results of the article [3] were first proved in a joint preprint with Xiaodong Cao [1].

中文翻译：

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更正为：三负曲率算子的爱因斯坦四流形

这是为了承认文章[3]的主要结果是在与曹小东[1]的联合预印本中首次得到证明的。