Introduction to non-linear mechanics / Kryloff,N. and N. Bogoliuboff ; a free translation by Solomon Lefschetz of excerpts from two Russian monographs. Non-linear mechanics. Kryloff,N. (Nikolaĭ Mitrofanovich), 1879-1955. Bogoli͡ubov, N. N. (Nikolaĭ Nikolaevich), author. Lefschetz, Solomon, 1884-1972, translator. Differential equations. Oscillations. 530.1 KRI A reprint of the Princeton University Press edition of 1947. Errata: p. 106. Bibliography: p. [100]-105. New York : Kraus Reprint Co., 1970. 1970. 1970 Text 106 p. : eng engrus Annals of mathematics studies ; no. 11 Annals of mathematics studies ; no. 11.