I recently came across a wonderful set of notes on mathematical writing. It is a set of notes written by students who took Knuth’s class on mathematical writing. The link is here. It’s wonderful to see the amount of thought that Knuth puts into his writing down to worrying about whether he should put commas to separate a big number like 1233843 (and whether the rules change when the number is inside a formula). The notes contain some funny anecdotes.