Book "Mathematics at 4 h. H. 3. Multiple integrals and their applications. Curvilinear integrals, surface integrals and their applications" by H. A. Kondratieff is a fascinating and deep dive into the world of multidimensional analysis, which will become an indispensable assistant for both students and teachers. This work is the third part of an extensive mathematics training course, in which the author masterfully reveals the complex concepts of multiple integrals and their practical applications. The book is addressed to a wide range of readers: from students of technical and natural science specialties to graduate students and university teachers . It will be of interest to those who seek to deepen their knowledge in the field of mathematical analysis and are looking for high-quality educational materials that contribute to a better understanding of the subject. If you are passionate about mathematics, physics, engineering or related sciences, then this book will be not only a useful textbook for you, but also a real source of inspiration. In the third part of Mathematics, Kondratiev focuses on multiple integrals that play a key role in solving problems of multidimensional geometry and physics. The author not only explains the theoretical aspects, but also demonstrates how these concepts are applied in real-world problems. The reader will be able to learn how to calculate curvilinear integrals as well as surface integrals, which is an important step in mastering more complex topics, such as Greene's theorem and Stokes' theorem. Kondratiev uses clear and accessible language, which makes the material understandable even for those who encounter these topics for the first time. Each section of the book is accompanied by examples and tasks that help to consolidate the knowledge gained and develop skills in solving practical problems. This makes the book not only a theoretical tool, but also a practical tool for self-study. The topics raised in the book cover a wide range of issues related to multidimensional integration. Kondratiev discusses how multiple integrals can be used to calculate body volumes, surface areas and other important characteristics in various fields of science and technology. It also touches on the application of these integrals in physics, such as electrodynamics and mechanics, making the material particularly relevant to students and professionals working in these fields. The author's style is distinguished by clarity and logical presentation, which allows the reader to easily follow the course of thought. Kondratiev is an experienced teacher and the author of several textbooks on mathematics, and his ability to explain complex things in simple language makes this book especially valuable. In the previous parts of his course, he has already considered the basics of mathematical analysis and differential equations, and now, in the third part, logically continues to develop the topic, deepening into more complex aspects. If you are looking for a high-quality and affordable guide to multiple integrals that will help you not only understand the theory, but also learn how to apply it in practice, then “Mathematics at 4 h. H. 3" by H. A. Kondratieff is what you need. This book will be your reliable companion in the world of multidimensional mathematics and will open up new horizons of knowledge for you. Do not miss the opportunity to immerse yourself in the exciting world of integrals and their applications, which can change your perception of mathematics and its role in science and life.