The theorem of van Kampen
17:42
The fundamental groupoid as a topological space
14:48
The fundamental group of the circle
1:16:52
Algebraic Topology 6: Seifert-Van Kampen Theorem
1:18:31
5. Induced Homomorphisms; van Kampen Theorem - Pierre Albin
10:08
The Seifert–Van Kampen Theorem
19:14
5.01 Van Kampen's theorem: statement and examples
14:50
Strange Pattern in symmetries - Bott periodicity
15:28