I am surprised this article does not mention Polya, who studied and taught heuristics in mathematics. His little classic How To Solve It -- from 1945! -- makes

I am surprised this article does not mention Polya, who studied and taught heuristics in mathematics. His little classic How To Solve It -- from 1945! -- makes recommendations that overlap a lot with the ones here. https://en.wikipedia.org/wiki/How_to_Solve_It https://en.wikipedia.org/wiki/How_to_Solve_It