Introduction to non-linear mechanics - Krylov, N. M. (Nikolai Mitrofanovich), 1879-1955.; Bogoliubov, N. N. (Nikolai Nikolaevich), 1909-; Lefschetz, Solomon, 1884-1972. (Princeton : Princeton University Press, 1947)
"2nd printing, 1947, with errata on p. 106".
MR