I was curious if anyone is aware of anything resembling a mathematical map, or learning tree. By this I mean a diagram that illustrates the sequence in which one must learn particular topics. I ask because I find myself encountering topics (today it was finite element method) and clicking the Wikipedia article, and finding that that article uses explanations dependent understanding other topics. Thus I work backwards through a series of articles until I find familiar subjects, and then work forward again. It would be nice to start with the stuff I know, and then move forward. Maybe this is a ridiculous idea.