1. Structural aspects of stability in non-linear systems Part I
2. Andronov, A. A., Vitt, A. A., and Khaikan, S. E., “Theory of Oscillators.” Pergamon, Oxford
3. Bryant, P. R., IEE Monograph 414E, London (November 1960).
4. On Non-Linear Differential Equations of the Second Order: I. the Equation y¨ − k
(1-y
2
)y˙ + y
= b
λk
cos(λl
+ α), k
Large