“…literature to derive suitable Lyapunov functions and hereby, in particular, many papers and books have been devoted to the study of stability and boundedness of solutions of certain second-, third-, fourth-, fi fth-and sixth order nonlinear differential equations (see, for example, Anderson [1], Barbasin [3], Cartwright [4], Chin ([5], [6]), Ezeilo ([8], [9]), Harrow ([10], [11]), Ku and Puri [13], Ku et al. [14], Ku ([15], [16]), Krasovskii [17], Leighton [18], Li [19], Marinosson [21], Miyagi and Taniguchi [22], Ogundare [23], Ponzo [24], Quian [25], Reissig et al [26], Schwartz and Yan [27], Shi-zong et al [28], Sinha ([29], [30]), Skidmore [31], Szegö [32], Tejumola ([33], [34]), Tiryaki and Tunç [35], Tunç ([36], [37], [38], [39], [40], [41], [42], [43]), Zubov [44], Wu and Xiong [45] and references quoted therein for some publications on these topics). So far, perhaps, the most effi cient tool for the study of the stability and boundedness of solutions of a given nonlinear differential equation is provided by Lyapunov theory.…”