12:48 Visual Group Theory, Lecture 1.6: The formal definition of a group 12:56 Discrete Homotopy Theory || First time in Pakistani YouTube channel 7:52 What is a Group? | A Visual Intro to Group Theory 6:07 Chapter 1: Symmetries, Groups and Actions | Essence of Group Theory 3:24 Visual Group Theory Shenanigans | April Madness #15 7:13 Теория визуальных групп Натана Картера 1:28 Visual Group Theory Podcast Episode 1