Atle Selberg's early work, which lies in the fields of analysis and number theory, concerns the Riemann zeta-function, Dirichlet's L-functions, the Fourier coefficients of modular forms, the distribution of prime numbers and the general sieve method. It is brilliant and unsurpassed, and is in the finest classical tradition. His later work, which cuts across function theory, operator theory, spectral theory, group theory, topology, differential...