This is a vintage textbook titled “Introduction to Non-Linear Mechanics” by Nikolai Mitrofanovich Krylov and Nikolai Nikolaevich Bogoliubov. It was published in 1950 by Princeton University Press as part of the “Annals of Mathematics Studies” series. The book is a trade paperback with 106 pages and is written in English. It covers the subject of mechanics and is aimed at students and scholars.