When I was a child, I loved to fill out things in workbooks and magazines for children. When I started going to school, I loved to fill out things in course- and workbooks and today I love doing so as well. No wonder, I have collected English coursebooks and workbooks throughout my whole education. Those were not only my personal ones, but I also have a collection of my brother's English coursebooks and some of my mother's as well. Some of my friends have also been so kind as to give me their coursebooks. So, as you can see, for us, (future) teachers, it can be pretty easy to get to materials on certain topics. And the best thing is that you can re-use these as many times as you want.