Construct a Borel set
3023
Construction of a Borel set with positive but not full measure in each interval
84394
Choice function for a collection of nonempty subsets of $\{0,1\}^\omega$
22482
How can an ordered pair be expressed as a set?
92571
Sets with no asymptotical density over $\mathbb N$
3870
A variation of Borel Cantelli Lemma
19289
complement of a set and its measure
151719
Connected set in $\mathbb{S}^1$
56370
Associative operation on a set $S$
90590
Prove that the following set is dense
22558
Vitali-type set with given outer measure
34964
Recursive representation of closed sets in Baire Space ($\Sigma^1_1$)
101028
Irrational numbers and Borel Sets
114929
Differences between the Borel measure and Lebesgue measure
11082
Borel-Cantelli Lemma "Corollary" in Royden and Fitzpatrick
24749
Monotone functions and Borel sets
104308
Proving a set is a Sigma Algebra
4213
The set that only contains itself