Thisbookisprimarilybasedonaone-yearcoursethathasbeentaughtforanumberofyearsatPrincetonUniversitytoadvancedundergraduateandgraduatestudents.DuringthelastyearasimilarcoursehasalsobeentaughtattheUniversityofMaryland.
WewouldliketoexpressourthankstoMs.SophieLucasandProf.RafaelHerrerawhoreadthemanuscriptandsuggestedmanycorrections.WeareparticularlygratefultoProf.BorisGurevichformakingmanyimportantsug-gestionsonboththemathematicalcontentandstyle.
Whilewritingthisbook,L.KoralovwassupportedbyaNationalSci-enceFoundationgrant(DMS-0405152).Y.SinaiwassupportedbyaNationalScienceFoundationgrant(DMS-0600996).