where the specific form of ͑Y , X 1 , X 2 , ͒, ͑Y , X 1 , X 2 , ͒, and ͑Y , X 1 , X 2 , ͒ is chosen to simplify the original system according to the five principles listed previously, and is found using an iterative procedure. To outline the procedure, we provide details for a simple example in Appendix A. Several iterations lead to coordinate transforms for U, V, and W along with evolution equations describing the Y-dynamics, X 1 -dynamics, and X 2 -dynamics in the new coordinate system. The Y-dynamics have exponential decay to the Y = 0 slow manifold. Substitution of Y = 0 leads to the coordinate transforms 