38:48

Lesson 3: Surfaces - Eulers Characteristic

32:27

Lesson 5: Surfaces - More Invariants

29:36

Lesson 8: Metric Spaces - Open Sets

24:38

Lesson 7: Metric Spaces - Definition and Examples

11:53

Benzene and Aromaticity: 4n+2, rule or guide?

16:31

Lesson 11 Compactness

23:26

Lesson 1: Topology Overview

10:10

Lesson 4: Surfaces - Orientation