As in the previous works, this new edition preserves the content, size, and convenience of this portable reference source for students and workers who use mathematics, while introducing much new material. New in this fourth edition is an expanded chapteron series that now includes many fascinating properties of the natural numbers that follow from number theory, a field that has attracted much new interest since the recent proof of Fermat’s last theorem. While the proofs of many of these theorems are deep, and in some cases still lacking, all the number theory topics included here are easy to describe and form a bridge between arithmetic and higher mathematics. The fourth edition also includes new applications such as the geostationary satellite orbit, drug kinetics (as an application of differential equations), and an expanded statistics section that now discusses the normal approximation of the binomial distribution as well as a treatment of nonlinear regression. The widespread use of computers now makes the latter topic amenable to all students, and thus all users of the Pocket Book of Integrals can benefit from the concise summary of this topic. The chapter on financial mathematics, introduced in the third edition, has proved successful and is retained without change in this edition, whereas the Table of Integrals has been reformatted for easier usage. This change in format also allowed the inclusion of all the new topics without the necessity of increasing the physical size of the book, thereby keeping its wide appeal as a true, handy pocket book that students and professionals will find useful in their mathematical pursuits.