Summary: Firstly a Lyapunov function is derived for
by applying the intrinsic method introduced by P. S. M. Chin [Int. J. Control 48, No. 4, 1561-1567 (1988; Zbl 0653.93038)]. Secondly equation (*) is examined in two cases: (i) , (ii) . For case (i) the asymptotic stability in the large of the trivial solution is investigated and for case (ii) boundedness results are obtained for solutions of equation (*). These results improve and include several well-known results.