1. Positive Linear Systems
2. Smith, H. (1995) Monotone Dynamical Systems: An Introduction to the Theory of Competitive and Cooperative Systems. Mathematical Surveys and Monographs, Vol. 41, Library of Congress Cataloging-in-Publication Data, Washington, DC.
3. Existence and stability of solutions of a delay-differential system
4. Liu, X., Yu, W. and Wang, L. (2009) Stability Analysis of Positive Systems with Bounded Time-Varying Delays. IEEE Transactions on Circuits and Systems II: Express Briefs, 56, 600-604.
5. Liu, X., Yu, W. and Wang, L. (2010) Stability Analysis for Contnuous-Time Positive Systems with Time-Varying Delays. IEEE Transactions on Automatic Control, 55, 1024-1028.