##### Chapter 4

^{1} Georg Friedrich Bernhard Riemann (1826–1866), great innovative German mathematician who made fundamental contributions to geometry and the theory of analytic functions of a complex variable to number theory, potential theory, topology and mathematical physics. His Riemannian geometry provides the foundation for modern relativity theory.

^{2} Cauchy, Augustin Louis (1789–1857), great French analyst, applied mathematician and group theorist. After Euler, the most prolific mathematician in history. He worked on wave, elasticity and group theory; introduced modern rigour into calculus, founded the theory of functions of a complex variable; inaugurated modern era in differential equations with his existence theorems.

^{3} Green, George (1793–1841), English analyst and applied mathematician.