This is a twist on revision notes. I have written some notes and given examples but there are mistakes that the students have to correct. They must therefore read the notes very carefully and a partner must check their work. The idea is derived from an idea born from a discussion on Twitter (if you're not on Twitter, seriously think about it). I have split the notes up into two bits but I have included the whole thing so that you can chop them up your own way, or change stuff if you want. It's a bit of an experiment and we&'ll see how it goes!