References:
Abstract Algebra - Wikipedia
https://en.wikipedia.org/wiki/Abstract_algebra
“Group theory, abstraction, and the 196,883-dimensional monster” - 3Blue1Brown
https://www.youtube.com/watch?v=mH0oCDa74tE
Axiomatic System - Wikipedia
https://en.wikipedia.org/wiki/Axiomatic_system
Axiom - Wikipedia
https://en.wikipedia.org/wiki/Axiom
Pure Mathematics - Wikipedia
https://en.wikipedia.org/wiki/Pure_mathematics
Group Theory - Wikipedia
https://en.wikipedia.org/wiki/Group_theory
Group (Algebra) - Wikipedia
https://en.wikipedia.org/wiki/Group_(mathematics)
Main Classes of Groups in Group Theory - Wikipedia
https://en.wikipedia.org/wiki/Group_theory#Main_classes_of_groups
Classification of Finite Simple Groups - Wikipedia
https://en.wikipedia.org/wiki/Classification_of_finite_simple_groups
Finite Group - Wikipedia
https://en.wikipedia.org/wiki/Finite_group
Lie-Type Group - Wolfram Mathworld
https://mathworld.wolfram.com/Lie-TypeGroup.html
Monster Group - Wikipedia
https://en.wikipedia.org/wiki/Monster_group
Monstrous Moonshine - Wikipedia
https://en.wikipedia.org/wiki/Monstrous_moonshine
J-invariant and Q-expansion - Wikipedia
https://en.wikipedia.org/wiki/J-invariant#The_q-expansion_and_moonshine
Continuous Symmetry - Wikipedia
https://en.wikipedia.org/wiki/Continuous_symmetry
Geometric Group Theory - Wikipedia
https://en.wikipedia.org/wiki/Geometric_group_theory