mathworld.wolfram.com
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MathWorld is an extensive online mathematics encyclopedia from Wolfram. It offers authoritative, easy-to-navigate articles on topics across mathematics, including set theory, its axioms, definitions, theorems, and related concepts, with links to related topics and illustrative figures.
More resources on Set Theory Axioms
PlanetMath: Zermelo-Fraenkel Axioms
Free encyclopedia entry on axioms
Stanford Encyclopedia of Philosophy: Axiomatic Set Theory
Comprehensive overview of set theory axioms
Set Theory
Learn set theory axioms with Peter Toth! Explore fundamental concepts in this comprehensive course.
plato.stanford.edu
The Stanford Encyclopedia of Philosophy is a peer‑reviewed online encyclopedia offering in‑depth, scholarly articles on philosophy, including topics like set theory, logic, and foundations of mathematics. Each article provides clear explanations, historical context, and extensive bibliographies for further reading.
ocw.mit.edu
MIT OpenCourseWare provides free, openly licensed MIT course materials—lecture notes, assignments, exams, and video lectures—across a wide range of subjects. It includes math and logic courses that cover topics like set theory, with freely downloadable resources and course overviews.
Set Theory
Set Theory - A book resource