Over the years I have been writing (very informal) notes on various mathematical topics, mostly for my own benefit. Even though these writings are far from attaining their finished form, I decided to make some of them available here, as they might be of use to potential readers. The material here is standard, drawn from a number of sources, so I make no claim to originality. Needless to say, I plan to keep polishing them whenever time permits, so stay tuned.