There are three different conceptions about base-level that are base level of erosion, base level of deposition and stratigraphic datum, respectively.

基准面有三个不同的概念，即侵蚀基准面、沉积基准面和地层基准面。

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Grubert and Altshuler have devised what many think is an elegant solution to both the competitiveness and the base erosion problems.

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So is this something that is really striking America as a whole, the erosion of the manufacturing base that started decades ago?

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How can the U.S. stop this erosion of the corporate tax base while keeping U.S.-based firms competitive in international markets?

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