Hi,there, I'm a college student of physics from China, and I've taken most undergrad physics course. when I tried to study some graduate-level books and some journal papers, I got a problem in math . In graduate level books (say, Jackson's for example), There are pages of math tricks I don't understand. I've taken a math-physics course and get some idea about Partial-diff equations and Bessel functions, etc. But when the equations can't use separate method, I don't know what to do with it. And in graduate level books, there are so many math tricks like magic. My question is : Where did they get these math techniques? Should I get a more advanced math-physics course? or should I stick on one grad-book like Jackson's, and work more harder on it. My college is not very good and it's hard to find a experienced person to ask. So I wonder is there anyone here who can do these math in ease will give me some help?