Construction of a Borel set
3023
Construction of a Borel set with positive but not full measure in each interval
63529
How to show that this set is compact in $\ell^2$
97064
Dense set in an infinite cofinite space
55717
cardinality of the Borel $\sigma$-algebra of a second countable space
146062
A "Cantor-Schroder-Bernstein" theorem for partially-ordered-sets
47937
Example of a Borel set that is neither $F_\sigma$ nor $G_\delta$
101028
Irrational numbers and Borel Sets
98580
Lebesgue-measurable sets requiring the Axiom of Choice to construct
125894
Prove that $\mathbb{Q}$ belongs to the Borel $\sigma$-algebra of $\mathbb{R}$
62687
Proving Cardinality of Cosets in Abstract Algebra
154474
Image of countable and uncountable sets
95294
Dense subset of $C[0,1]$ which preserves rationals
59424
Showing that $B=\{(x,y) \in \Bbb{R^2} \mid \ xy>0 \}$ is an open set
68230
The cardinality of a countable union of sets with less than continuum cardinality
103717
Topological Property of the Set of Integers
16892
Reference request: product Borel $\sigma$-algebra of non-separable metric spaces
134983
Borel sigma algebra not containing all subsets of $\mathbb{R}$?