The critical relations are the building blocks of the relational clone of a relational structure with respect to the relational operations intersection and direct product. In this paper we describe the critical relations of crowns. As a consequence, we obtain that the subpower membership problem for any crown is polynomial-time solvable.

中文翻译：

---

冠状病毒抑郁症关键时期牙冠的关键关系

关键关系是关于关系操作交集和直接乘积的关系结构的关系克隆的构建块。在本文中，我们描述了牙冠的关键关系。因此，我们得到任何冠的次幂隶属度问题是多项式时间可解的。