Corollary 2
Tag 0BX1, permanent. Cite it as [Bourbaki, Tag 0BX1].
General Topology, chapter VI, § 2. Euclidean distance, balls and spheres
The circle is homeomorphic to the torus .
In Chapter VIII, § 2, no. 1, we shall obtain this result again as a consequence of a more precise theorem.
Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.