“…V(x(t), y(t), z(t), w(t)) Define the Lyapunov function V V(x(t), y(t), z(t), w(t)) by Then, by the analysis in [7], V(0,0,0,0) g(y(t)) < ala2 ly(t)l; and f(z(t)) < a2a3/a4. Therefore, dlg'(y(t)) dzf(Z(t)) a 2 (+I/al)g'(y(t)) ( Given any solution (x,y,z,w) of (2.5)…”