Harmless delays in a discrete ratio-dependent periodic predator-prey system. Fan, Yong-Hong, Li, Wan-Tong (2006) Discrete Dynamics in Nature and Society
Hopf bifurcation for simple food chain model with delay. Cavani, Mario, Lara, Teodoro, Romero, Sael (2009) Electronic Journal of Differential Equations (EJDE) [electronic only]
Hopf bifurcation for the equation x ¨ ( t ) + f ( t ) ) x ˙ ( t ) + g ( x ( t - r ) ) = 0 · . Acosta, Antonio, Lizana, Marcos (2005) Divulgaciones Matemáticas