This volume is dedicated to the eminent Russian mathematician Igor Borisovich Simonenko on the occasion of his 70th birthday. The contributions are written by leading experts and present the state of the art in a number of areas originally initiated in pioneer works by I. B. Simonenko. Among the topics covered are Fredholm theory for singular integral and convolution operators, estimates for singular integral operators on Carleson curves acting in Lp spaces with variable exponents, the finite section method for band-dominated and Toeplitz operators, Szegö-type theorems, and the averaging method for nonlinear equations. The book testifies to the wide mathematical interest of I. B. Simonenko and includes a biography, his list of publications and a list of his Ph.D. students.