$\newcommand{\NN}{\mathbb{N}}$
$\newcommand{\ZZ}{\mathbb{Z}}$
$\newcommand{\RR}{\mathbb{R}}$
$\newcommand{\CC}{\mathbb{C}}$
$\newcommand{\pr}{^\prime}$
$\newcommand{\prpr}{^{\prime\prime}}$
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Holes
Spaces and their Maps
Surfaces
One-dimensional Holes
Two-dimensional Holes
The Hopf Fibration
Spheres and co-Spheres
Multiplicative Structures
References
Batterman --- Why Equilibrium Statistical Mechanics Works --- 1998