1. Les cycles limites de poincaré et la théorie des oscillations autoentretenues;Andronov;Comptes Rendus,1929
2. Bellman, R. (1964). Perturbation Techniques in Mathematics, Physics and Engineering. Holt, Rinehart and Winston, Inc.
3. Bellman, R. and Richardson, J.M. (1963). Closure Techniques for Infinite Systems of Differential Equations. CA: RAND Corporation, Santa Monica.
4. A history of infinite matrices;Bernkopf;Archive for History of Exact Sciences,1968
5. Buonomo, A. and Schiavo, A.L. (2002). Analyzing the dynamic behavior of rf oscillators. IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications.