Hi :) Okay so next month I have an exam in the course Mathematical Methods III and I desperately need a good textbook to study from. We covered variation calculus,fourier analysis and partial differential equations including sphrical harmonies (legendre polynomials) and various boundary problems. This course was very intense and the problem sets were extremely difficult. We were assigned Arfken's Mathmatical Methods for physicists book but I find it very hard to work with it. I'm looking for books about the subjects mentioned above that have CLEAR AND SIMPLE explanations that would fit an undergraduate student and a variety of problems and exercises in different difficulty levels. Thanks a lot!!!