20. Some Sources:
Donald Norman
Jef Raskin
Jacob Nielsen
Bruce "Tog" Tognazzini
I recommend all the talks by Alan Kay and Bret Victor, here's two:
Doing with Images Makes Symbols
https://www.youtube.com/watch?v=p2LZLYcu_JY
The Future Of Programming
https://www.youtube.com/watch?v=8pTEmbeENF4
The first 8 items of this thread are extremely terse, to the point of being meaningless on their own. Please use them as search terms, or ask me to expand on them when my dog isn't barking at me to go to bed.