Physics -- paper and pencil, in the late 1980s, at Harvard. Books such as Purcell, "Electricity and Magnetism", Reif, "Fundamentals of Statistical and Thermal Physics", Liboff, "Introductory Quantum Mechanics", Sakurai, "Modern Quantum Mechanics", Ashcroft and Mermin, "Solid State Physics", Brown and Churchill, "Complex Variables and Applications", and "Fourier Series and Boundary Value Problems".