Hi, while self-studying physics, I keep bumping into books that transition into more abstract math, using notation systems unfamiliar to me. This is often accompanied by explanations consisting of: 'we can write this as' 'it is easy to show that' 'therefore', which are not particularly helpful. And as books usually build on earlier sections, this is usually the point where I have to abandon a work. And of course, the next book reexplains all the sections I did understand, until again suddenly descending into some rune-language. Are there any good methods/places to become familiar with these notation systems? Unfortunately I don't have access to professors who can explain the tricky bits when questions arise. My focus would mostly be on SR/GR, and the problem usually starts appearing around the point where more abstract objects containing multiple elements, such as matrices, start appearing in formulas with millions of indices.