The purposes, level, and style of this new edition conform to the tenets
set forth in the original preface. We continue with our tack of developing
simultaneously theory and applications, intertwined so that they refur-
refurbish and elucidate each other.
We have made three main kinds of changes. First, we have enlarged on
the topics treated in the first edition. Second, we have added many
exercises and problems at the end of each chapter. Third, and most
important, we have supplied, in new chapters, broad introductory discus-
discussions of several classes of stochastic processes not dealt with in the first
edition, notably martingales, renewal and fluctuation phenomena associ-
associated with random sums, stationary stochastic processes, and diffusion
theory.