The Riddle That Seems Impossible Even If You Know The Answer - Veritasium
https://www.youtube.com/watch?v=iSNsgj1OCLA
The unbelievable solution to the 100 prisoner puzzle - Stand-up Maths
https://www.youtube.com/watch?v=a1DUUnhk3uE
FACE REVEAL - The 1M Subs Q&A - Steve Mould
https://www.youtube.com/watch?v=GLADzZJqEyI
Main channel over here: https://www.youtube.com/standupmaths
And here is that paper: https://doi.org/10.1007/BF02986999
Legit free copy: https://www.cl.cam.ac.uk/~gw104/Locker_Puzzle.pdf