00361nam a2200133 a 450000500170000002000150001708200160003210000200004824500550006826000360012330000200015949000330017970000150021220251203110134.0  a0387974911  a515.35bBOG  aBogaevski, V.N.  aAlgebraic methods in nonlinear perturbation theory  aNew YorkbSpringer-Verlagc1991  axii,265p.c22cm  aApplied mathematical science  aPovzner, A