The lowercase letters in (6) denote the concentrations of the uppercase letters in (1)- . Notice equations (6a)-(6b) are autonomous and independent of s 2 and c 2 . In this regard, the first catalyzed reaction drives the second catalyzed reaction; thus, the indicator reaction can be viewed as a non-autonomous system with forcing term k 2 c 1 (t). Moreover, since lim t→∞ c 1 = 0, the vector field that governs the flow of the indicator reaction is asymptotically autonomous .