[1] M. Adivar, M. Islam and Y. N. Raffoul, Existence of periodic and
positive periodic solutions in totally nonlinear delay differential
equations, submitted.
[2] E. R. Kaufmann and Y. N. Raffoul, Periodic solutions for a neutral
nonlinear dynamical equation on a time scale, J. Math. Anal. Appl.
319(1) (2006), 315-325.
[3] E. R. Kaufmann and Y. N. Raffoul, Periodicity and stability in
neutral nonlinear dynamic equations with functional delay on a time
scale, Electron. J. Differential Equations 27 (2007), 12.
[4] Y. N. Raffoul, Periodic solutions for neutral nonlinear
differential equations with functional delay, Electron. J.
Differential Equations 102 (2003), 1-7.
[5] Y. N. Raffoul, Positive periodic solutions in neutral nonlinear
differential equations, E. J. Qualitative Theory of Diff. Equ. 16
(2007), 1-10.
[6] D. R. Smart, Fixed Points Theorems, Cambridge Univ. Press,
Cambridge, 1980.