I have learnt Calculus (single and multi-variable) Ordinary Differential equations (upto 2nd order linear with Laplace transforms, including Dirac Delta functions and Fourier Series. I have not learnt series solutions nor special functions which I see is the next step in this chapter) Linear Algebra (self-taught from Hoffman and Kunze. I have not completed this however. Am still continuing) Have done the Calculus of Variations chapter from Boas Math Methods My math is physics oriented. I hope to start reading Goldstein's book this fall, followed by E&M, QM, Stat Mech etc. in the following years. What math should I learn now? Tensors? Group theory? Pick up where I left off from ODEs and continue to PDEs? Complex analysis? Could you also suggest textbooks for the respective chapters?