“…The Lyapunov inequality and its generalizations have been used successfully in connection with oscillation and Sturmian theory, asymptotic theory, disconjugacy, eigenvalue problems and various properties of the solutions of (1) and related equations, see for instance [57,29,5,12,13,14,17,18,25,31,35,36,38,39,40,41,44,48,49,50] and the references cited therein. For some of its extensions to Hamiltonian systems, higher order differential equations, nonlinear and half-linear differential equations, difference and dynamic equations, functional and impulsive differential equations, we refer in particular to [17,18,15,16,21,22,23,24,27,28,20,32,34,42,43,45,46,47,51,53,54,55,56,58]. Further, no more Lyapunov and Hartman type inequalities are known for higher-order nonlinear differential equations.…”