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This category contains results about Sigma-Rings.
Definitions specific to this category can be found in Definitions/Sigma-Rings.

A $\sigma$-ring is a ring of sets which is closed under countable unions.

That is, a ring of sets $\Sigma$ is a $\sigma$-ring if and only if:

$\ds A_1, A_2, \ldots \in \Sigma \implies \bigcup_{n \mathop = 1}^\infty A_n \in \Sigma$


This category has only the following subcategory.


Pages in category "Sigma-Rings"

The following 3 pages are in this category, out of 3 total.