I suggest big parts of Paul's Online Notes to students who need some brush-up or remediation. When I was teaching college precalc, for instance, people usually

I suggest big parts of Paul's Online Notes to students who need some brush-up or remediation. When I was teaching college precalc, for instance, people usually had a reasonable grasp of y=mx+b but difficulties with exponentiation were almost universal. Some of these "cheat sheets" are useful for such students just to tape above their workspace so that while working through the rote mechanical practice problems they must do they can use the "cheat sheet" as a checklist while they work. The review of complex numbers, on the other hand (not a cheat sheet but a condensed review) I assign to some masters' students who have not used complex numbers for 2 years and need to recall what they once learned. There it's just a concise but reasonably comprehensive refresher list.