Usage of $\epsilon$ in Naive Set Theory by Paul R. Halmos
50258
How can a set contain itself?
72185
The negation of a limit condition, Spivak style.
92390
The meaning of notation $\subset\subset$ in complex analysis
95042
Textbooks on set theory
120712
Is there a way to define the "size" of an infinite set that takes into account "intuitive" differences between sets?
84251
Show that $\Gamma \cup \{\neg \phi\}$ is satisfiable if and only if $\Gamma\not \models \phi$
23442
Cardinality of the union of infinite and countable sets
27600
Gödel's (in)completeness theorems and the axiomatization of Euclidean geometry
109054
Given an infinite set of cardinality $X$, is there a chain in $\mathcal P(X)$ of the same cardinalty of $\mathcal P(X)$?
81509
The cardinality of a countable union of countable sets, without the axiom of choice
108922
Cardinality and infinite sets: naturals, integers, rationals, bijections
120252
Equivalences of bounded sets definitions
120188
Why is the real line not used in Descriptive Set Theory?
52451
Ordered Triples and Set Theory
152976
Real Analysis: open and closed sets
80255
How to prove that $|a-b|<\epsilon$ implies $|b|-\epsilon<|a|<|b|+\epsilon$?
140868
Axiomatization of $\mathbb{Z}$ via well-ordering of positives.