Every Closed Hypersurface is Orientable
137071
Orientation of hypersurface
76496
Showing that every field is an integral domain.
122050
Algebraic extension of perfect field in which every polynomial has a root is algebraically closed
2198
Maps from subsets of $\mathbb{R}^2$ that are either open/closed/continuous
148685
Equivalences of definitions of submanifolds in $\mathbb{R^n}$
66895
A condition for the image of a metrizable space to be metrizable
49703
Analogue of closed graph theorem
88981
Explicit Homeomorphism from $\mathbb{R}^2$ to open disk
81550
Linking two theorems: on algebraic closure and on minimal splitting field
108394
Proof of that every interval is connected
64502
On the meaning of being algebraically closed
154682
G/H is Hausdorff implies H is closed (General topology, Volume 1 by N. Bourbaki)
97669
Sheafs and closed immersion
44623
Closed set as a countable intersection of open sets
33734
Every closed subset $E\subseteq \mathbb{R}^n$ is the zero point set of a smooth function
123656
Covering map between orientable compact connected surfaces without boundary with genus $g$
136106
Is every open subset of $ \mathbb{R} $ uncountable?