Recap exercises

I just put out a set of exercises to fresh up your hands-on experience with index notation -- which can be a nice thing to do for those of you who already want to start going a bit. These exercises will be discussed, along with any other questions or comments that you may have about the required background material, during the first group exercise session on 23/01.
(Note hence that we start with the group exercises already during the first lecture week, unlike what is stated in the course plan on the semester page)