1. Hierarchical aggregation of linear systems with multiple time scales
2. Perturbation Theory for Linear Operators
3. KOKOTOVIC , P. V. ( editor ), 1980 , Coordinated Science Laboratory Rep. R.901 , University of Illinois .
4. LUSE , D. W. , and KHALIL , H. K. , 1983 ,Proc. Automatic Control Conf., San Francisco . pp. 443 – 144 .