SEARCH Articles Figures Tables Approximate Nonlinear Lumping in Systems with Timescale Separation Approximate lumping in systems with time-scale separation Approximate non-linear lumping in systems with time-scale separation Asymptotic approximation nonlinear systems Bilateral Approximations to Periodic Solutions of Systems with Lag Born approximation systems Born-Oppenheimer approximation systems Coherent potential approximation systems studied Dynamical systems Quasi-Steady State Approximation Finite-basis approximations. Closed-shell systems Markov approximation systems Polyatomic Systems in Approximation The Cell Model Rotating-wave approximation system Three-Phase System and Linear Approximation Tunneling in Jahn-Teller Systems and Multidimensional WKB Approximation