1. In advanced mathematics, especially in multiple integrals and multiple differentials, there is a structure called "integral tower" or "integral formula tower". It is used to solve problems involving multiple integrals and differentials.

2. In higher geometry, especially in Euclidean geometry and non-Euclidean geometry, there is a structure called "axiom tower" or "axiom system". It is used to establish the basic axioms and theorems of geometry.

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