1. R. Bellman, K. L. Cooke;Differential-Difference Equations. Academic Press, New York, 1963.
2. A. Fischer; On stability radii of infinite-dimensional continuous-time positive systems. In preparation.
3. D. Hinrichsen, A. J. Pritchard; Real and complex stability radii: a survey. In: D. Hinrichsen, B. Mårtensson (eds.),Control of Uncertain Systems, pp. 119?162. Birkhäuser, Boston, 1990.
4. D. Hinrichsen, N. K. Son; Stability radii of positive discrete-time systems under affine parameter perturbations. Report No. 373, Institute for Dynamical Systems, University of Bremen, 1996.
5. P. Meyer-Nieberg;Banach Lattices. Springer-Verlag, Berlin, 1991.