1. Optimal control problems in Banach spaces;Balakrishnan;J. Siam Control Ser. A,1965
2. Infinite Dimensional Filtering;Curtain;J. Siam Control,1975
3. The Infinite Dimensional Riccati Equation, in Recent Mathematical Developments in Control Theory;Curtain,1972
4. A linear control problem in abstract Hilbert space;Datko;J. Differential Equations,1971
5. Perturbation Theory for Linear Operators;Kato,1966