Chapter 92: Galois theory
https://www.youtube.com/watch?v=BSHv9Elk1MU
https://www.youtube.com/watch?v=3imeTgGBaLc
https://www.youtube.com/watch?v=1EWUsef0iFs
https://www.youtube.com/watch?v=Ct2fyigNgPY
Aleph 0 = Aleph Null
https://www.youtube.com/watch?v=CwvuZ8aHyH4
https://www.youtube.com/watch?v=9aUsTlBjspE
https://www.youtube.com/watch?v=zCU9tZ2VkWc
https://www.bilibili.com/video/BV1vS411P7DV