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#### OhMyMarkov

##### Member

- Mar 5, 2012

- 83

We let E denote the family of all elementary subsets of $R^p$... E is a ring, but not a $\sigma$-ring.

According to my understanding of what a $\sigma$-ring is, it is the union of infinitely many sets $A_i$, each belongs to this ring. In "slang" mathematical terms, given any subset in $R^p$, we can describe it as the union of infinitely many subsets in $R^p$.

Any help is appreciated!