“…x (5) (t) + A 1 x (4) where x ∈ , t ∈ + , + = [0, ∞), A 1 , A 2 , A 3 , A 4 and A 5 are not necessarily constants. For a comprehensive treatment of the subject we refer the reader to the papers of Ezeilo [4][5][6], Li and Duan [10], Li and Yu [11], Sadek [14], Sun and Hou [15], Tiryaki [16], Tunç [17][18][19], Tunç and Erdogan [21], Tunç and Karta [22], Tunç and Şevli [23] and the references cited in these papers for some works performed on the subject, which include some fifth order nonlinear differential equations without delay.…”