1. The Diffusion Equation.- 2. Laplace's Equation.- 3. The Wave Equation.- 4. Linear Second-Order Equations with Two Independent Variables.- 5. The Scalar Quasilinear First-Order Equation.- 6. Nonlinear First-Order Equations.- 7. Quasilinear Hyperbolic Systems.- 8. Approximate Solutions by Perturbation Methods.- A.1. Review of Green's Function for ODEs Using the Dirac Delta Function.- A.2. Review of Fourier and Laplace Transforms.- A.3. Review of Asymptotic Expansions.- References.