This paper discusses the asymptotic stability for a well-known time-variant system by means of the direct method of Liapunov. The system exhibits a positive time-invariant Liapunov function with negative semi-definite derivative. The paper focuses on the extra conditions needed in order to guarantee asymptotic stability. The proposed criterion is compared with the results available in the literature.
93C99, 93D20, 93D05, 93B30, 34H05, 34D99