1. Acosta A., Lizana M.: Hopf bifurcation for the equation $${\ddot{x}(t) + f (x(t))\dot x(t) + g(x(t -r)) = 0}$$ x ¨ ( t ) + f ( x ( t ) ) x ˙ ( t ) + g ( x ( t - r ) ) = 0 . Divulgaciones Matematicas. 13, 35–43 (2005)
2. Balachandran, B., Kalmár-Nargy, T., Gilsinn, D.E.: (eds) Delay Differential Equations. Recent Advances and New Directions, Springer, New York (2009)
3. Benevieri P., Calamai A., Furi M., Pera M.P.: Global branches of periodic solutions for forced delay differential equations on compact manifolds. J. Differ. Equ. 233(2), 404–416 (2007)
4. Benevieri P., Calamai A., Furi M., Pera M.P.: On forced fast oscillations for delay differential equations on compact manifolds. J. Differ. Equ. 246(4), 1354–1362 (2009)
5. Benevieri, P., Calamai, A., Furi, M., Pera, M.P.: Global continuation of periodic solutions for retarded functional differential equations on manifolds. Bound. Value Probl. 2013(21), 1–19 (2013)